oil & mpg
I just changed my oil on an engine with 141k miles to mobil 1 extended mileage 5w30, and my mpg dropped at least 10%, what gives?
I'm pretty sure it was running conventional 5-30 before, but the manual called for either. This is a Nissan 3.0 V6, but it's making me wonder about what I put in my LS1 (redline 5w30).
I would really appreciate a little explanation.
Tom

