My 2008 Silverado "Vortec Max" 6.0 calls for 5w30 year round. To sum things up quickly, I have installed an aftermarket computer tune, and an aftermarket exhaust system. I drive this truck HARD including heavy towing, and also some off road fun (sand-dunes) Do you oil guru's think I should still stick with the 5w30? I am running the highly popular Pennzoil platinum...and have not bothered with a UOA yet due to break-in. I now have just over 27,000 miles on her. I was thinking going to PP 10w30 in the summer due to the slightly better NOACK, and slightly better HTHS numbers. I know that these factory hand held tuners can create more stress on engines, and am looking for anyone in the same boat as me who has done UOA's on slightly modified engines to chime in.