WHOA! 10w40?!
isn't that a little too thick?
could be losing power for those racing junkies, and gas mileage for those daily drivers?
think of a 5w30/20 as a softball going through the oil passages...now think of 10w40 as a beachball. which one is going to slip through easier? And this was quoted by the geniuses at Royal Purple.
I personally run 5w30 Synthetic. Just my kind of fancy. And plus from what I've learned in class, chosing the wrong oil religiously could lead to premature failure of the engine, even if you are trying to go for a thicker oil to slow down any kind of oil leaks you have.