IMO, the choice of
oil and change intervals is one of the most controversial subjects in motorsports. What works vs. what doesn't, heavy vs. light,
synthetic vs. dino. I've done a lot of reading on this subject over the years, and here's my "conclusions":
1. Weight - use the factory/engine builders recommendations. Differant materials and differant build techniques matter. You can adjust pressure a little bit by changing the weight, but not a lot. But using a 20W-50
oil in an engine designed for 5W-20 is going to cause problems.
2. What works: They all do. Some are better than others, but there doesn't appear to be any significant differance beween, say, Castrol and Penzoil. But there is probably a differance between Penzoil and K-Mart brand.
3.
Synthetic: Engines usually gain a little power with it so there must be a little less friction. Therefore, it must be slipperier (???) Sounds good on paper, doesn't it? But really, I think the big advantage to
synthetic oil is it's resistance to heat. Heat will significantly reduce the effectivness of the oil to do it's many jobs. Every heat spike reduces the oils ability. Add enough of them together, and you have a problem. So I use synthetic in everything I drive.
4. Change Interval: This probably causes more contoversy than anything else. People say every 3K. Why? because that's the way their daddy did it. Well, your daddy wasn't driving a 2004 BMW. Modern engines, modern technology, modern materials, and modern oils are far differant than they were in 1965.
First, read your owners manual. For my wifes Mercury Cougar, it's every 7.5K Miles. Second, look at how you use the car. Third, look at the oil you're using. More frequent oil changes do not do anything for the performance or longevity of your engine.
You need to understand not only what you're doing, but why you're doing it. Do you change it because it's dirty? No, your filter keeps it clean. You change it because the additive package gets used up, and the oil breaks down because of heat and physical trauma. If you use a top shelf oil, and drive the engine easily, that oil will last a long time.
That's my opinion, and you're welcome to it
