Im looking at doing an oil change at some point this week, the last twice i have used comma xtech 5w30 as recomended by subaru, what im wondering is, is this what i should be puting in, my car is 2004 wrx that has been modded and produces 280bhp but the car has also done 95,000 miles, should i be looking at using a thicker oil, a fully synthetic or semi synthetic etc, or am i ok sticking to what im using, the car uses about 1 litre of oil every 1000 miles or so.