Originally Posted By: WishIhadatruck
I have a 1.4T in a Cruze also. I've always run 5w30 PP, but I wonder if the 0w30 would give better fuel economy when cold?
Yes it would. But only below about 25 degrees F would the Mobil 1 0w30 give better MPG in my estimation based on the Widman Visc Calc and assuming the PPD and VII in the 0w30 has a non-newtonian effect when getting very cold. Actually, the Pennzoil Platinum 5w30 has a higher VI ! VI is figured on KV40 and KV100, which is warm and hot, where the 0w30 formulation doesn't show any MPG benefit and is thicker than the Pennzoil Platinum 5w30.
As the engine warms up from very very cold, I give the MPG advantage to the 0w30. Anything above around freezing (0degC), Pennzoil Platinum 5w30 wins.