One thing to consider if you use synth-oil in regard to the manufacturers' BS about 25,000 miles between changes- You got a 5 qt. crankcase and start out with your, say, $4-5 per quart synth-oil. In normal consumption of like a quart just every 2,000 miles how do you end up with the same oil you started with? It fakes you out into thinking "yeah its more expensive but it'll last 25,000 miles so it's cheaper in the long run." In 25,000 miles you'd have bought an additional 15 quarts over the 5 you started with. Bogus!