Originally Posted By: Patman
Originally Posted By: Capa
I recently went from an 0W-40 to a 0W-20 in a V8 and have seen around 8% MPG gain, which I wouldn't call a tiny improvement.
Most of that gain is probably from the recent switchover from "winter gas" to the summer blend, which always results in higher MPG anyways.
Im not sure that we get winter blend here and the AC has been blasting in my car for those fill ups, unlike the previous fill ups. I would expect about an 8% gain going down two oil grades. Note that I am not recommending this to the OP, I just thought that I would share my experience.