How does thinner oil generate better gas mileage?Mazda calls for 5w-30 in the 2.5 NA for the rest of the world. It's only in the US and Canada that Mazda says use 0w-20. It's pretty much only for slightly better mpg
I mean this 0w-20 stuff is pretty runny.
It seems to me (based on pure conjecture and no scientific data on my part) that oil this thin offers less protection than 5w-30, and possibly shortens the life of the engine over the long haul.
I remember a certain contributor from a few years ago (now banned) that swore his engine ran better on 5w-30. I might just go that route when I do my spring oil change later this month.