You would think that 5w-50 would be thick, but since it was full synthetic its very non-viscus. I can't tell a difference between the Syntec 5w-50 and 5w-30 so I've never been too worried. However, best milage on a tank to date was on 5w-50. I don't think once you go full synthetic it really matters much between synthetics for mileage.

I did try 0w-30 Castrol Syntec full synthetic in my wife's Eclipse Spyder this winter and that stuff poured out like water.