Chevy 350, nothing special due to the restrictions for the class. This is my buddies car and he has been running dino 20w50 for the season. Would delo 15w40 be okay to try for this because of the robust add pack? Or should he stick with a 10w30 or 40? I can't remember what the chevy 350 was spec'd for. 20w50 just seems too heavy for this application. He cahnges the oil out every 10 races so there is not a lot of miles on the oil just several short WOT runs. Thanks for help!