mystery machine Posted March 23, 2011 Share Posted March 23, 2011 As I understand — or misunderstand, as the case may be — both of the above will offer the same performance at higher temperatures, but the 5w40 will perform better at lower temperatures... But if that's the case, then why would anyone ever opt for the 10w40...? I know I'm missing something here, and I'm intrigued to find out what Can anyone offer enlightenment? Cheers Link to comment
kennyuk300 Posted March 23, 2011 Share Posted March 23, 2011 As I understand — or misunderstand, as the case may be — both of the above will offer the same performance at higher temperatures, but the 5w40 will perform better at lower temperatures... But if that's the case, then why would anyone ever opt for the 10w40...? I know I'm missing something here, and I'm intrigued to find out what Can anyone offer enlightenment? Cheers Well hi ,the 10w will be better in colder conditions W= Winter ... Kenny Link to comment
mystery machine Posted March 23, 2011 Author Share Posted March 23, 2011 (edited) Well hi ,the 10w will be better in colder conditions W= Winter ... Kenny Cheers for the reply Kenny, but I'm 99% sure that the lower the first number the better in colder conditions... Question is, if 5W is better in colder conditions, and they're both equally rated at 40 for higher operating temperatures, why would you ever want the 10W? Is 5W simply too thin for some engines, even in the cold? Edited March 23, 2011 by Mystery Machine Link to comment
kennyuk300 Posted March 23, 2011 Share Posted March 23, 2011 Cheers for the reply Kenny, but I'm 99% sure that the lower the first number the better in colder conditions... Err i am 99% certain you are right Ok i made a mistake trying to type, eat dinner and build Duplo lol.... I would say you can change it as the weather heats up Kenny Link to comment
mystery machine Posted March 23, 2011 Author Share Posted March 23, 2011 (edited) Ok i made a mistake trying to type, eat dinner and build Duplo lol.... Edited March 23, 2011 by Mystery Machine Link to comment
greensleeves102 Posted March 23, 2011 Share Posted March 23, 2011 (edited) Cheers for the reply Kenny, but I'm 99% sure that the lower the first number the better in colder conditions... Question is, if 5W is better in colder conditions, and they're both equally rated at 40 for higher operating temperatures, why would you ever want the 10W? Is 5W simply too thin for some engines, even in the cold? not 100% sure but i think the further away the two numbers are from each other the faster the oil breaks down eg a 0w 40 will break down faster than a 10w 40 etc hope this helps Edited March 23, 2011 by greensleeves102 Link to comment
robert_harding Posted March 23, 2011 Share Posted March 23, 2011 (edited) a usefull link for you. scroll to the bottom. http://www.opieoils.co.uk/pdfs/tech-articles/Engine-Oil-Viscosity.pdf then this one. http://www.opieoils.co.uk/pdfs/tech-articles/Multigrade-Oils.pdf Edited March 23, 2011 by mean&green Link to comment
rig-pig Posted March 23, 2011 Share Posted March 23, 2011 The SAE classifications characterises the viscosity at low and high temperature of the lubricant. The grade is given by two numbers separated by the letter W (meaning winter). The first number, followed by W represents the low temperature viscosity, 5W, 10W, 15W... the lower this number, the more fluid at low temperature the oils, the easier the engine starts. The second number gives the high temperature viscosity: 30, 40, 50. The higher this number, the more viscous the oil when hot 10w40 is fine all year round here m8 Link to comment
mystery machine Posted March 24, 2011 Author Share Posted March 24, 2011 (edited) Thanks for the replies, and the links m&g. The meaning of the cold/hot weight ratings is very clear to me, but I still haven't been able to ascertain why anyone would opt for 10w40 over 5w40 (although there may well be a good reason!). I was trying to decide which spec oil to use at the Scoob's next service. Ended up buying some Millers CFS 5w40 – hopefully a step up from Castrol Magnatec 5w30. Edited March 24, 2011 by Mystery Machine Link to comment
fmj Posted March 24, 2011 Share Posted March 24, 2011 (edited) Surely oil can be too thin or too thick. 10w40 may give better protection at start up when 5w40 may be too thin for the cold engine. Then again 10w40 could be too thick in very cold weather to pump around as easily as the 5w40 making the 5w40 better... Both are within the manufacturers guidelines so its personal choice. Maybe most use 10w40 as it's more generally available, also it says so its fine in the book so why not? I really cant afford to buy expensive oil every six months and have been using castrol magnatec since I brought my scooby five years ago with no problems even after remapping and tuning. Some people get very elitist and anal about things like oil... but if you can afford it why not, I guess I would too. I do for example use V power exclusively but then my car has been remaped for it so it makes it worth it. Edited March 24, 2011 by FMJ Link to comment
StanS Posted March 24, 2011 Share Posted March 24, 2011 I was confused about oil and so have done a bit of reading and am less confused. It did take about 30 mins to read the following link (8 pages), but worth it if you REALLY want to try to understand what is going on. Its not straight forward as there are so many factors. Temp/pressure/flow rates/viscocity - around pages 6/7 IIRC. I needed to read from the start to make sure I was not using stuff I had "heard". http://www.bobistheoilguy.com/cms/index.php?option=com_content&view=article&id=83 I think my Motul 300V comp 15W50 is wrong for my engine and I think I should be on 5W40 or a 5W30. Phone call to my oil man tomorrow ! Link to comment
Chris180883 Posted March 24, 2011 Share Posted March 24, 2011 Whats peeps opinions on millers cfs 10/60 ??? Link to comment
HairyDJ Posted March 24, 2011 Share Posted March 24, 2011 Oilman posted back in January here I've decided to drop from 10w50 to 5w40 next purchase based on his advice Link to comment
paulcoleman Posted March 26, 2011 Share Posted March 26, 2011 When I first got my non-turbo I put 10w40 in by accident, and acceleration was sluggish in the cold, noticeably. Swapped it a week later for 5w40 (Motul Xcess 1800 I think from Opie Oils) and it ran much better, so I use 5w40 every time now. I think 10w is thicker at cooler temps, but I gather some older cars cant keep the 5w in as its thinner and escapes through finer gaps that develop in older engines. A friend of mine years ago had an old Nova which he ran 10wXX with no oil leaks at all. Bought 0wXX for performance and it was coming out the bottom of the engine as fast as it was going in the top!! I think this is why some people with older engines would choose 10w over 5w. I noticed better/smoother acceleration in my old Mk2 Mondeo when switching from 10w to 5w as well, but it weeped a bit of oil from somewhere, but not enough to worry about. HTH. Paul Link to comment
mystery machine Posted March 28, 2011 Author Share Posted March 28, 2011 I think 10w is thicker at cooler temps, but I gather some older cars cant keep the 5w in as its thinner and escapes through finer gaps that develop in older engines. A friend of mine years ago had an old Nova which he ran 10wXX with no oil leaks at all. Bought 0wXX for performance and it was coming out the bottom of the engine as fast as it was going in the top!! I think this is why some people with older engines would choose 10w over 5w. Interesting – I can see the sense in that Link to comment
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