Oilman

I never said it was rubbish, just that you can buy better. An ester/pao like Silkolene PRO S is in a different league to it, that's all. Cheers Simon

<< Oilman - how does the price work? You posted prices for 2x5litres and 4x5litres, is that per person or as a total for the group? If it includes delivery I assume each individual would have to order 2x5litres to get it for that price? Cheers >> Currently those are the prices each if you order 2x5 or 4x5. (These are our Clubs Oil Scheme prices) Delivery and vat is included in those prices for each individual to their front door. Depending on the level of orders, I may be able to give everyone the 4x5 litre price but we'll see how it goes. Cheers Simon

<< Simon - I stated in the SN thread that I would like 2 x 5l of 10w50 Pro S. Only thing is my service is on Thursday. How can we work this out ? Cheers Ben >> Just call me and we'll sort something out 01209 215164 Cheers Simon

OK, that's good. Lets get some numbers together and we'll talk prices. For starters: Silkolene PRO S 5w-40, 10w-50 or PRO R 15w-50 2x5 litres £61.69 4x5 litres £108.49 Prices include deliver by Amtrak Mainland UK Can also offer other products by Castrol, Mobil, Total and Silkolene but you'll need to let me know what you're after. Hope this helps Cheers Simon

Thanks. Firstly I would feel happier if a group buy was endorsed by the Club or the Admins here, perhaps someone could get in touch with me so that we can get the club officially signed up to our "clubs oil scheme". Regarding selection of grade. If your car is stock and not of the older type i.e. post 1996 use 5w-40 If your car is modded in any way (bhp wise), used for trackdays, of the older type (pre 1996) oe high mileage use 10w-50. Either oil will work well in the scoob but the heavier weight oil tends to quieten older ones down. Hope this helps. Cheers Simon

I would strongly recommend: Silkolene PRO S 5w-40 or 10w-50 depending on your set up and driving style. I could start a "group buy" here if permitted? Cheers Simon

Basically, you can do soooo much better if you choose to Cheers Simon

Glad to see someone's using the good stuff! Cheers Simon

Great oil that - for cooking! Cheers Simon

<< Does anyone know what Subaru will use as standard if nothing else is specified? That's what's in mine, anyway... Thanks, Jim >> Jim, It is generally down to individual dealers, they tend to sign up with one supplier or another to provide all their oils, could be Castrol, Mobil, Comma, and the list goes on. Cheers Guy.

The recommended oil is 5w-40 so the one you are using is on the "heavy" side of correct. I would recommend the Ester/PAO based PRO S 5w-40 as the first choice as it's a shear stable 5w-40 and can operate for prolonged periods up to 130 degC although it's ideal operating range is 90-110 degC. If you're really not comfortable with 5w-40 then use 10w-50 but I think this is "overkill" viscosity wise. I've emailed you a price list. Cheers Simon

It depends what your're using the car for as it's a good semi-synthetic but bear in mind that it's not in the same league as the Silkolene PRO range for durability (petroleum vs synthetics) if you are doing track days or competitive driving. You will pay a lot less for the XTR 10w-40 but it will need changing more frequently so you need to weigh up the costs. Cheers Simon

No problemo! Bike oils contain different additive packages to cope with clutch slip etc and therefore are slightly different. You could use a bike oil in a car but not the other way around however, we don't recommend it. Cheers Simon

I don't recommend or sell it either. I would however recommend Castrol Performance 10w-40 Silkolene XTR 10w-40 Fuchs XTR 10w-40 Total Quartz 7000 10w-40 The VI's on these are all good between 149 and 155 which indicates the quality of the bsestocks used. Before you ask the highest is the XTR at 155. Cheers Simon

Just drop me an email for price list sales@opieoils.co.uk You will find technical data sheets here: http://www.opieoils.co.uk/lubricants.htm Hope this helps Cheers Simon

<< so after all that it is decided that we should go for a 10w50 oil? is this silkoline rs good then?? and how often should the oil be changed?? >> Your handbook will give a range of useable viscosities (10w-60 does not appear) but depending on the Model/Year it will be either 5w-40 or 10w-40 for our climate in the UK. The reasons for using Silkolene PRO S 10w-50 are if you use your car for trackdays etc in which case its a far better oil than 10w-60. OEM Quotes the following oils Impreza 1.6i, 1.8i (4WD) 1993-96 10w-40 / 10w-50 Impreza 1.6 (4WD) 2000 onwards 5w-30 / 5w-40 Impreza 2.0i Sport 1996-00 5w-40 / 10w-40 / 10w-50 Impreza 2.0 (4WD) 2000 onwards 5w-30 / 5w-40 Impreza 2.0i Turbo (4WD) 1994-00 5w-40 Impreza 2.0i WRX/STi Turbo (4WD) 2001 onwards 5w-40 Impreza 2.0 Turbo (4WD) 2000 onwards 5w-40 Impreza 2.5i (4WD) 2001 onwards 5w-40 Hope this helps, Cheers Simon

<< However, real world experience of people like Bob Rawle and others cannot be taken with a pinch of salt. >> I'm not discounting the advice of people like Bob Rawle and have had some debates on Scoobynet with him about the use of 10w-60 as I cannot find anywhere that Subaru recommend an SAE 60. The fact is it would be unproffessional of me to recommend an oil that the OEM does not recommend in their handbooks. << I think Im going to go with 10w 50, as I dont rag my car very often. I do a few cold starts a day, and several long motorway journeys per week, totalling 25 to 30,000 miles per year. >> Interesting comment this as if I interpret it correctly, you equate thickness with protection and this is not necessarily the case I'm afraid. As stated before it's about "shear stability" and quality a non "true" synthetic 10w-60 will only be operating as an sae 40 within a couple of thousand miles whereas a "true" synthetic will stay in grade for 9-12,000 miles therefore a proper 10w-50 fully synthetic will be affording more protection at high temps for longer. Please also consider my comments concerning the damage that can be caused by using an oil that is too thick and in my opinion sae 60 is just too thick. The oils mentioned in your handbooks will be 5w-40, 10w-40 or 10w-50 look for yourself and you'll see. << Am i doing the right thing ? I want to change the oil as infrequently as possible, but without risk. What about a 5w 50 ? Are they available ? >> Yes you are, let the mechanics stick to their job and the "oilmen" do theirs, you would even get benefits from using a PAO/Ester based 5w-40. 5w-50 is not a regularly available viscosity but I have 1 PAO based one. Your better off using a 5w-40 instead as it is not such a wide viscosity oil and needs less additives to prop it up. At the end of the day, it's personal choice but 10w-60 is not the correct oil for your car. Cheers Simon

No problems, any questions on oil please feel free to ask, I'm watching this topic so I'll get back to you. Cheers Simon

Drop me an email or PM me. Cheers Simon

We recommend Silkolene PRO S 5w-40 and 10w-50 for your cars and if you've read the article "Lubricating a Subaru" you will understand the reasons why. If not then here are some good reasons for not using an sae 60 (apart from the fact it's not recommended by Subaru themselves) which you should take into consideration. Before I start yes we sell Castrol products but do not recommend RS 10w-60 for your cars, there is a difference as we work on technical recommendations from OEM databases. 1. It's simply too thick. It's really too thick and, even hot-running engines do not need SAE 60 oil these days. (by ?hot? I mean 120-130C). SAE 60 is heavier than most SAE 90 gear oils. If an oil is too thick, it de-aerates slowly, leading to cavitation in the oil pump, or the bearings being fed slugs of air along with the oil. 2. The 10w-60 product in question is not a "true" synthetic, it's a hydrocracked, petroleum based mineral oil which quite franky is not in the same league as Mobil 1, Silkolene PRO S or R, Redline etc. If you are intending to use your car in a "spirited" fashion or do the odd "track day" then "shear stability" is the key as you need an oil that is more thermally stable. The problem with wide viscosity petroleum oils is that they need buckets of VI Improver to prop them up which makes them prone to "shearing". This is not the case for "true" synthetics. SAE has a test called HT/HS (High Temperature/High Shear) API ASTM D4683 tested at 150 degC. The higher the HT/HS number the better because this indicates less shearing. Petroleum oils tend to have low HT/HS numbers which barely meet the standards set by SAE. Because petroleum oils are made with light weight basestocks to begin with, they tend to burn off easily in high temperature conditions which causes deposit formation and oil consumption. As a result of excessive oil burning and susceptibility to shearing (as well as other factors) petroleum oils must be changed more frequently than synthetics. Not all multi-viscosity oils shear back so easily. True synthetic oils (PAO?s and Esters) contain basically no waxy contamination to cause crystallization and oil thickening at cold temperatures. In addition, synthetic basestocks do not thin out very much as temperatures increase. So, pour point depressants are unnecessary and higher viscosity basestock fluids can be used which will still meet the "W" requirements for pumpability. Hence, little or no VI improver additive would need to be used to meet the sae 30, 40 or 50 classification while still meeting 0W or 5W requirements. The end result is that very little shearing occurs within true synthetic oils because they are not "propped up" with viscosity index improvers. There simply is no place to shear back to. In fact, this is easy to prove by just comparing synthetic and petroleum oils of the same grade. Synthetics will generally have significantly higher HT/HS numbers. Of course, the obvious result is that your oil remains "in grade" for a much longer period of time for better engine protection and longer oil life. So, what is VI Improver? As a lubricant basestock is subjected to increasing temperatures it tends to lose its viscosity. In other words, it thins out. This leads to decreased engine protection and a higher likelihood of metal to metal contact. Therefore, if this viscosity loss can be minimized, the probability of unnecessary engine wear will be reduced. VI improvers are polymers that expand and contract with changes in temperature. At low temperatures they are very compact and affect the viscosity of a lubricant very little. But, at high temperatures these polymers "expand" into much larger long-chain polymers which significantly increase the viscosity of their host lubricant. So, as the basestock loses viscosity with increases in temperature, VI improvers ?fight back? against the viscosity drop by increasing their size. The higher the molecular weight of the polymers used, the better the power of "thickening" within the lubricant. Unfortunately, an increase in molecular weight also leads to an inherent instability of the polymers themselves. They become much more prone to shearing within an engine. As these polymers are sheared back to lower molecular weight molecules, their effectiveness as a VI improver decreases. Unfortunately, because petroleum basestocks are so prone to viscosity loss at high temperatures, high molecular weight polymers must be used. Since these polymers are more prone to shearing than lower molecular weight polymers, petroleum oils tend to shear back very quickly. In other words, they lose their ability to maintain their viscosity at high temperatures. Synthetic basestocks, on the other hand, are much less prone to viscosity loss at high temperatures. Therefore, lower molecular weight polymers may be used as VI improvers. These polymers are less prone to shearing, so they are effective for a much longer period of time than the VI improvers used in petroleum oils. In other words, synthetic oils do not quickly lose their ability to maintain viscosity at high temperatures as petroleum oils do. In fact, some synthetic basestocks are so stable at high temperatures they need NO VI improvers at all. Obviously, these basestocks will maintain their high temperature viscosities for a very long time since there are no VI improvers to break down. 3) I cannot find any OEM recommendations that list 10w-60 as a grade you can use and you need to follow these first when selecting the correct oil for your car. On many newer vehicles only 0w-40, 5w40 or 10w40 engine oils are recommended by the manufacturer. If you choose to use a higher viscosity oil than what is recommended, at the very least you are likely to reduce performance of the engine. Fuel economy will likely go down and engine performance will drop. In the winter months it is highly recommended that you not use a heavier grade oil than what is recommended by the manufacturer. In cold start conditions you could very well be causing more engine wear than when using a lighter viscosity oil. In the summer months, going to a heavier grade is less of an issue, but there are still some things to be aware of. Moving one grade up from the recommended viscosity is not likely to cause any problems (say from a 10w40 to a 10w50 oil). The differences in pumping and flow resitance will be slight. Although, efficiency of the engine will decrease, the oil will likely still flow adequately through the engine to maintain proper protection. However, it will not likely protect any better than the lighter weight oil recommended by the manufacturer. Moving two grades up from the recommended viscosity (say 10w40 to 10w-60) is a little more extreme and could cause long term engine damage if not short term. Although the oil will still probably flow ok through the engine, it is a heavier visocosity oil. As such it will be more difficult to pump the oil through the engine. More friction will be present than with a lighter viscosity oil. More friction will be present than with a lighter viscosity oil. More friction means more heat. In other words, by going to a thicker oil in the summer months, you may actually be causing more heat build-up within the engine. You'll still be providing adequate protection from metal to metal contact in the engine by going with a high viscosity, but the higher viscosity will raise engine temperatures. In the short run, this is no big deal. However, over the long term, when engine components are run at higher temperatures, they WILL wear out more quickly. As such, if you intend on keeping the vehicle for awhile, keep this in mind if you're considering using a heavier weight oil than the manufacturer recommends. The best advice is to is to stay away from viscosity grades that are not mentioned in your owner's manual or consult a specialist oil suppier. There it is then. Cheers Simon

Here's some guidance on selecting the correct oil for your car. "Surely the thicker the oil the better!" This isn't always true - even when using a petroleum oil. Although it is true that heavier viscosity oils (which are generally thought of as being thicker) will hold up better under heavy loads and high temperatures, this doesn't necessarily make them a better choice for all applications. On many newer vehicles only 0w-40, 5w40 or 10w40 engine oils are recommended by the manufacturer. If you choose to use a higher viscosity oil than what is recommended, at the very least you are likely to reduce performance of the engine. Fuel economy will likely go down and engine performance will drop. In the winter months it is highly recommended that you not use a heavier grade oil than what is recommended by the manufacturer. In cold start conditions you could very well be causing more engine wear than when using a lighter viscosity oil. In the summer months, going to a heavier grade is less of an issue, but there are still some things to be aware of. Moving one grade up from the recommended viscosity is not likely to cause any problems (say from a 10w40 to a 10w50 oil). The differences in pumping and flow resitance will be slight. Although, efficiency of the engine will decrease, the oil will likely still flow adequately through the engine to maintain proper protection. However, it will not likely protect any better than the lighter weight oil recommended by the manufacturer. Moving two grades up from the recommended viscosity (say 10w40 to 10w-60) is a little more extreme and could cause long term engine damage if not short term. Although the oil will still probably flow ok through the engine, it is a heavier visocosity oil. As such it will be more difficult to pump the oil through the engine. More friction will be present than with a lighter viscosity oil. More friction means more heat. In other words, by going to a thicker oil in the summer months, you may actually be causing more heat build-up within the engine. You'll still be providing adequate protection from metal to metal contact in the engine by going with a high viscosity, but the higher viscosity will raise engine temperatures. In the short run, this is no big deal. However, over the long term, when engine components are run at higher temperatures, they WILL wear out more quickly. As such, if you intend on keeping the vehicle for awhile, keep this in mind if you're considering using a heavier weight oil than the manufacturer recommends. The best advice is to is to stay away from viscosity grades that are not mentioned in your owner's manual as these are the most suitable for your engine. Cheers Simon

John Rowlands very informative article mentions the labelling issues regarding synthetic oils briefly but here's more detail regarding the mess that the US court ruling has created! Due to the court case in the states between Mobil and Castrol, you may not always be getting what you think you are so be careful, hydrocracked oils are not synthetics in the true sense of the word as they are molecularly converted petroleum oils, synthetics are not, they are built by chemists in laboratories "brick by brick" and are far superior. Unfortunately, apart from in Germany, a manufacturer can label the inferior "hydrocracked" oils as synthetics and therefore the only true way of working out the quality is price although even this is not certain as there are some very expensive "hydrocracked" oils out there which are sold on their brand name, Castrol is a good example as they were the Company that Mobil took to court over the labelling issues. Here is some more reading for those interested: ?HYDROCRACKED? (HC) or MOLECULARLY CONVERTED (MC) BASESTOCKS There are many petroleum oils available on the market that are so pure and refined, they can now be passed off as synthetics. They are not made from true synthetic basestocks (at least not in the way that synthetics have traditionally been defined), but they have so little in common with traditional petroleum basestocks, it is really somewhat silly to classify them as petroleum oils. Petroleum oil basestocks can be put through a super-extreme refining process called ?hydrocracking?. In some cases, as in the case of one particular name-brand "synthetic" oil, these highly refined petroleum basestocks can actually be termed and sold as "synthetic". It is completely legal for lubricants manufacturers to label these oils as "synthetic". These are extremely high performance petroleum basestocks, but they are not truly synthetic the way that most people understand the term and will not necessarily perform to the same level as a premium synthetic oil like PAO (poly alfa olefins) or Esters. Hydrocracking involves changing the actual structure of many of the oil basestock molecules by breaking and fragmenting different molecular structures into far more stable ones. This results in a basestock which has far better thermal and oxidative stability as well as a better ability to maintain proper viscosity through a wide temperature range - when compared to a typical petroleum basestock. Although contaminants are still present, and these are still petroleum basestocks, contamination is minimal and performance characteristics are high. This process also can turn a wider range of crude oil stock into well-performing petroleum lubricant basestocks. TYPES OF SYNTHETIC BASESTOCKS Synthetic basestocks are not all the same. There are few different chemical types that may be used as synthetic basestock fluids. There are only three that are seen commonly in automotive applications: Polyalphaolefins (PAO's) These are the most common synthetic basestocks used in the US and in Europe. In fact, many synthetics on the market use PAO basestocks exclusively. PAO's are also called synthesized hydrocarbons and contain absolutely no wax, metals, sulfur or phosphorous. Viscosity indexes for nearly all PAO's are around 150, and they have extremely low pour points (normally below ?40 degrees F). Although PAO's are also very thermally stable, there are a couple of drawbacks to using PAO basestocks. One drawback to using PAO's is that they are not as oxidatively stable as other synthetics. But, when properly additized, oxidative stability can be achieved. Diesters These synthetic basestocks offer many of the same benefits of PAO's but are more varied in structure. Therefore, their performance characteristics vary more than PAO's do. Nevertheless, if chosen carefully, diesters generally provide better pour points than PAO's (about -60 to -80 degrees F) and are a little more oxidatively stable when properly additized. Diesters also have very good inherent solvency characteristics which means that not only do they burn cleanly, they also clean out deposits left behind by other lubricants - even without the aid of detergency additives. They do have one extra benefit though, they are surface-active (electrostatically attracted to metal surfaces), PAO?s are not ?polar?, they are ?inert?. Polyolesters Similar to diesters, but slightly more complex. Greater range of pour points and viscosity indexes than diesters, but some polyolester basestocks will outperform diesters with pour points as low as -90 degrees F and viscosity indexes as high as 160 (without VI additive improvers). They are also ?polar?. Other synthetic basestocks exist but are not nearly as widely used as those above - especially in automotive type applications. Most "proper" synthetics on the market will use a single PAO basestock combined with an adequate additive package to provide a medium quality synthetic lubricant. However, PAO basestocks are not all the same. Their final lubricating characteristics depend on the chemical reactions used to create them. Premium quality synthetics will blend more than one "species" of PAO and/or will blend these PAO basestocks with a certain amount of diester or polyolester in order to create a basestock which combines all of the relative benefits of these different basestocks. This requires a great deal of experience and expertise. As a result, such basestock blending is rare within the synthetic lubricants industry and only done by very experienced companies. In addition, although such blending creates extremely high quality synthetic oils, they don't come cheap. You get what you pay for! Or do you? Cheers Simon

This is probably the longest post on this Forum but certainly one of the most interesting and relevant to all Subaru Owners. It is the "FULL" unedited transcript of the article written by John Rowland (Chief R&D Chemist for Silkolene) with 40 years experience. It is great educational reading as it is written by a Chemist, not a Salesman so totally based in facts - If you do one thing, read this, it's worth it! Please note that I do not work for Silkolene and I have Johns express permission to post this article to clear up as he would term "the mis-information" on the internet. I am however in the oil business. LUBRICATING THE SUBARU. Basically Basically, to use that irritating in-word, engine lubrication is simple, and consequently boring. So I intend to treat the subject ?complicatedly?, which may not be an in-word, but makes life far more interesting! So, to take a quick look at the simple picture; the oil keeps moving parts apart, reducing friction and carrying away heat. Where there is metal-to-metal contact there are chemicals in the oil to reduce damage. Because the internal combustion process is always less than perfect, some soot is produced and this must be washed off the pistons and rings by the oil, so it has a cleaning or detergent function as well. The trouble is, all this is just as true for Henry Ford?s original Model T engine as it is for the Subaru or any other high output motor. So where is the difference? The Model T, with 10bhp/litre at 2,000rpm and a single underhead camshaft, was filled with a thick, greenish liquid from somewhere near the bottom of the distillation colums on the Pennsylvania oilfields. It did a vague tour of the internals by guesswork (there was no oil pump) at a temperature around 50 degC, and lasted for 1,000 miles. On the plus side, some of the impurities acted as anti-wear and detergent chemicals. They didn?t work very well, but it was better than nothing. The engine wore out in around 20,000 miles, but even ordinary people, not just amateur rally drivers, were happy to put up with this. The difference begins with the first turn of the key. The modern high-pressure pump would cavitate on the old heavy monogrades, starving the bearings for a vital couple of seconds, even in warm weather. Likewise, cam lobes would suffer as the sluggish oil found its way along narrow oil ways to the valve gear. The turbo bearing (if fitted as the handbooks say) already spinning fast, would also starve, and when it got going, how long would it be before the heat soak-back fried the primitive oil into a lump of carbon? (This was the problem with ?modern? oils only 15 years ago). So, a good oil must be quite low in viscosity even in the cold, so that it gets around the engine in a fraction of a second on start-up. On the other hand, it must protect engine components (piston rings for example) at temperatures up to 300 degC without evaporating or carbonising, and maintain oil pressure. Unmodified thin oils simply can?t manage this balancing act. The answer is to use a mixture of thin oil and temperature-sensitive polymer, so as the thin oil gets even thinner with increasing temperatures as the engine warms up, the polymer expands and fights back, keeping the viscosity at a reasonable level to hold oil pressure and film thickness on the bearings. This is called a multigrade. But, this is all too basic! What I have just written was and is relevant to a 1958 Morris Minor. The questions that Subaru owners need to ask are: ?Will this thin oil evaporate and be drawn into the intake manifold (via the closed circuit crankcase ventilation), leading to combustion chamber deposits and de-activated catalysts?? and ?Will the polymer shear down at high engine revolutions and high temperatures, causing low oil pressure and component wear?? and ?Will it carbonise on the turbo bearing?? These are 21st century questions which cannot be answered by a basic 1990?s approach. BUT! Before we head into more complications, some figures??? The SAE Business (American Society of Automotive Engineers) Viscosity is the force required to shear the oil at a certain speed and temperature. Oils work because they have viscosity; the drag of a rotating part pulls oil from a low-pressure area into a high pressure area and ?floats? the surfaces apart. This is called ?hydrodynamic lubrication?, and crank bearings depend on it. In fact a plain bearing running properly shows literally no metal-to-metal contact. Experimental set-ups have shown that electrical current will not flow from a crank main bearing to the shells. Also, the energy loss due to friction (the co-efficient of friction) is incredibly low, around 0.001. So for every kilogram pulling one way, friction fights back with one gram. This is very much better than any ?dry? situation. For example, the much over-rated plastic PTFE has a co-efficient of friction on steel of 0.1, 100 times worse than oil. Oil viscosities are accurately measured in units called ?Centistokes? at exactly 100 degC. These fall into five high temperature SAE catagories:- SAE No. 20 30 40 50 60 Viscosity Range 5.6 - <9.3 9.3 - <12.5 12.5 - <16.3 16.3 - <21.9 21.9 - <26 A decent quality oil usually has a viscosity that falls in the middle of the spec, so a SAE 40 will be about 14 Centistoke units, but SAE ratings are quite wide, so it?s possible for one 40 oil to be noticeably thicker or thinner than another. When the polymer modified multigrades appeared, a low temperature range of tests were brought in, called ?W? for winter (it doesn?t mean weight). These simulate cold starta at different non-ferrous monkey endangering temperatures from ?15 degC for the 20w test to a desperate ?35 degC for 0w. So, for example, an SAE 5w-40 oil is one that has a viscosity of less than 6600 units at ?30 degC, and a viscosity of about 14 units at 100 degC. Now, those of you who have been paying attention will say ?Just a minute! I thought you said these multigrade polymers stopped the oil thinning down, but 6600 to 14 looks like a lot of thinning to me!?. Good point, but the oil does flow enough to allow a marginal start at ?30 degC, and 14 is plenty of viscosity when the engine is running normally. (A lot more could damage the engine. Nobody uses the 24 viscosity SAE 60 oils any more.) The vital point is, a monograde 40 would be just like candle wax at ?30 degC, and not much better at ?10 degC. It would even give the starter motor a fairly difficult time at 0 degC. (At 0 degC, a 5w-40 has a viscosity of 800 but the monograde 40 is up at 3200!) Another basic point about wide ranging multigrades such as 5w-40 or 0w-40 is that they save fuel at cruising speeds, and release more power at full throttle. But complications arise??.. Building a good oil A cave may not be the best place to live, but it?s ready-made and cheap. This is the estate agent?s equivalent of an old style monograde oil. Or you could get Hengist Pod to fit a window and a door; this is moving up to a cheap and cheerful mineral 20w-50. But an architect-designed ?machine for living in?, built up brick by brick, is an allegory of a high performance synthetic oil. It is impossible to make a good 5w-40, or even 10w-40, using only mineral oil. The base oil is so thin, it just evaporates away at the high temperatures found in a powerful engine that is being used seriously. Although there are chemical compounds in there to prevent oil breakdown by oxygen in the atmosphere (oxidation) they cannot adequately protect vulnerable mineral oil at the 130 degC plus sump temperatures found in hard worked turbocharged or re-mapped engines. Synthetics are the answer. They are built up from simple chemical units, brick by brick so as to speak; to make an architect-designed oil with properties to suit the modern engine. But sometimes, if you look behind the façade, there is a nurky old cave at the back! This is because the marketing men have been meddling! The Synthetic Myth What do we mean by the word ?synthetic?? Once, it meant the ?brick by brick? chemical building of a designer oil, but the waters have been muddied by a court case that took place in the USA a few years ago, where the right to call heavily-modified mineral oil ?synthetic?, was won. This was the answer to the ad-man?s dream; the chance to use that sexy word ?synthetic? on the can?.without spending much extra on the contents! Most lower cost ?synthetic? or ?semi-synthetic? oils use these hydrocracked mineral oils. They do have some advantages, particularly in commercial diesel lubricants, but their value in performance engines is marginal. TRUE synthetics are expensive (about 6 times more than top quality mineral oils). Looked at non-basically there are three broad catagories, each containing dozens of types and viscosity grades:- PIB?s (Polyisobutanes) These are occasionally used as thickeners in motor oils and gear oils, but their main application is to suppress smoke in 2-strokes. The two important ones are: Esters All jet engines are lubricated with synthetic esters, and have been for 50 years, but these expensive fluids only started to appear in petrol engine oils about 20 years ago. Thanks to their aviation origins, the types suitable for lubricants (esters also appear in perfumes; they are different!) work well from ?50 degC to 200 degC, and they have a useful extra trick. Due to their structure, ester molecules are ?polar?; they stick to metal surfaces using electrostatic forces. This means that a protective layer is there at all times, even during that crucial start-up period. This helps to protect cams, gears, piston rings and valve train components, where lubrication is ?boundary? rather than ?hydrodynamic?, i.e. a very thin non-pressure fed film has to hold the surface apart. Even crank bearings benefit at starts, stops or when extreme shock loads upset the ?hydrodynamic? film. (Are you listening, all you rally drivers and off road fanatics?) Synthetic Hydrocarbons or POA?s (Poly Alpha Olefins) These are, in effect, very precisely made equivalents to the most desirable mineral oil molecules. As with esters, they work very well at low temperatures, and equally well when the heat is on, if protected by anti-oxidants. The difference is, they are inert, and not polar. In fact, on their own they are hopeless ?boundary? lubricants, with LESS load carrying ability than a mineral oil. They depend entirely on the correct chemical enhancements. PAO?s work best in combination with esters. The esters assist load carrying, reduce friction, and cut down seal drag and wear, whilst the PAO?s act as solvents for the multigrade polymers and a large assortment of special compounds that act as dispersants, detergents, anti-wear and oxidant agents, and foam suppressants. Both are very good at resisting high-temperature evaporation, and the esters in particular will never carbonise in turbo bearings even when provoked by anti-lag systems. Must Have MORE Power! Motorcars are bought for all sorts of reasons, but enthusiasts like lots of power. To get more power, a lot of fuel must be burnt, and more than half of it, sadly, gets thrown away as waste heat. For every litre of fuel burnt, 60% of the energy goes as waste heat into the exhaust and cooling system. A turbocharger can extract a few percent as useful energy and convert it into pressure on the intake side, but only 40-45% is left, and only 25% actually shows up as BHP at the flywheel. 6% goes in pumping air into the engine, 6% as oil drag losses and 2-3% as engine friction. The oil deals with 97% of the friction; so reducing the remaining few percent is not easy. If you doubt that even ordinary oil has a massive effect, take a clean, dry 200 bhp engine, connect it to a dyno and start it up. It will only make 1 bhp for a few seconds. Now that?s real friction for you! Oddly enough, people get starry-eyed about reducing friction, especially those half-wits who peddle silly ?magic additives?, which have not the smallest effect on friction but rapidly corrode bearings and wallet contents. In fact, even a virtually impossible 50% reduction in the remaining engine friction would be no big deal, perhaps one or two bhp or a couple of extra miles per gallon. Even More Power! He place to look for extra power is in that 6% lost as oil drag. In a well-designed modern motor, the oil doesn?t have to cover up for wide clearances, poor oil pump capacity or flexy crankshafts, so it can be quite thin. How thin? Well take a look at these dyno results. A while ago now, we ran three Silkolene performance oils in a Honda Blackbird motorcycle. this fearsome device is fitted with a light, compact, naturally aspirated 1100cc engine which turns out 120+ bhp at the back wheel. The normal fill for this one-year-old engine was 15w-50, so the first reading was taken using a fresh sump-fill of this grade. (The dyno was set up for EEC horsepower, i.e. Pessimistic) 15w-50 Max Power 127.9 bhp @ 9750 rpm Torque 75.8 ft-lbs @ 7300 rpm After a flush-out and fill up with 5w-40 the readings were; 5w-40 Max Power 131.6 bhp @ 9750 rpm Torque 77.7 ft-lbs @ 7400 rpm Then we tried an experimental grade, 0w-20 yes, 0w-20! This wasn?t as risky as you may think, because this grade had already done a season?s racing with the Kawasaki World Superbike Team, giving them some useful extra power with no reliability problems. (But it must be said, they were only interested in 200 frantic miles before the engines went back to Japan) 0w-20 Max Power 134.4 bhp @ 9750 rpm Torque 78.9 ft-lbs @ 7400 rpm In other words, 3.7 bhp / 2.9% increase from 15w-50 to 5w-40, a 2.8 bhp / 2.1% increase from 5w-40 to 0w-20 or a 6.5 bhp / 5% overall. Not bad, just for changing the oil! More to the point, a keen bike owner would have paid at least £1000 to see less improvement than this using the conventional approach of exhaust/intake mods, ignition re-mapping etc. Am I recommending that you use 0w-20 in your Subaru?s? Well, perhaps not! The 5w-40, which is a ?proper? PAO/Ester shear-stable synthetic, will look after a powerful engine better than a heavier viscosity ?cave at the back? conventional oil, and provide a useful extra few BHP. The End However, as with all good things in life, we don?t live in a world of perfect motor cars and therefore we have to look at the lubrication trade-off between longevity, reliability, power and cost, relative to the vehicle in which the oil is being used (a scruffy old XR2i with 192,000 miles on the clockis a very different proposition to your spanking new Impreza). Which is why Subaru (and probably your local dealer) recommends a 10w-50 (Such as PRO S); you could look at a 5w-40 for competition and track-day use, but only the most committed competitor would want, or need, the 0w-20 for the extra 5% power. Cheers Simon