I own an 88 s15 with a 2.8L v6. The engine is fairly new and only has 30,000 miles on it. It doesnt burn any noticable amount of oil. My problem is choosing the right multigrade for it. When I drive it hard the oil thins to nothing and the lack of pressure makes me nervous. But, on the other hand when it is chilly ouside the oil takes a second to make it up on the topside of the engine and I get alot of valve train noise (in the winter, summer is ok). Currently I am using Castrol GTX 10w30. I was thinking of maybe going to a 15w30 or 20w40 for the summer. As for the winter, I am lost. What are yall's suggestions?