The HART (Honda of America racing team) all run Redline oil in their cars. I race with a couple of the engineers. Most of the time the OEM recommended viscosity, but the ICE engineers recommend Redline oil. They use it in the transmission and differential as well. Gives some accreditation that a Japanese auto manufacturer uses Redline oil for there performance driving teams. I'll ask the GM Performance Driving team next time I see them to ask what oil they use. For me it makes sense just to use the OEM viscosity, but not be concerned with the API or emissions related oil specifications that Dexos and others are held to. OEM oil grades with top notch lubrication qualities.