Car 1: 2001 Z06 Corvette with approx. 440 rwhp. - 84,xxx miles Former HPDE car 4-5x a year, but now retired to nice weather commuter and weekend toy. Ran M1 5w30 initially but started experimenting w/ thicker oils when oil consumption became and issue. Had the car re-ringed in 2004 under warrnty and switched to M1 0w40 at that time. Eventually I switched to Amsoil 5w40 w/ a K&N filter and have run that for years. Last weekend I went back to a M1 extended performance filter and regular M1 synthetic 5w30 simply because the car isn't tracked anymore and the M1 is available right down the street vs. ordering. The car will get the oil changed ever 5k or once a year I guess. Car 2: 2004 GMC Canyon DD/Toy hauler - 57,xxx miles I inherited this from my grandfather in early '07 with 11k on it. I have been using M1 extended performance 5w30 and the M1 filter with 10k changes just becuase it's easy to remember. Amazingly this truck doesn't use a drop of oil in between 10k changes, it has 57k on it now and will be up for another change at 60k. I'm used to adding a little bit of oil ever few thousand miles in my LS6 (Corvette motor). Thoughts? Part of me says I should put the extended performance in both cars and do both once a year or every 10k. Part of me says I should go back to Amsoil in the Corvette but go w/ the 0w30 fancy stuff, but even w/ my preferred customer discount it's still mighty expensive these days. Thanks all.... BTW this forum drives me nuts! Every subject has 11,000,000 different answers!