[Shane@DBPerformance]

10w40 on any built motor or any motor making decent power. I would only run 5w30, if recommended by the manufacturer, on a 100% stock car that wasn't modded. Running too thin of oil is one of the biggest motor killers. We run 10w40 mixed with 20w50 on high HP motors. M1 5w30 is the cause of more spun rod bearings than I can count, seen it on 4Gs, 2Jzs, Subarus, Hondas, Mustang motors, SR20s, etc...