I do not know what other have experienced. I have been using Mobile One for about 4000 miles now. There has not been any change in my mileage sense I changed to Mobile One. My mileage variations are in direct relation to my driving habits.
I switched to Mobil 1 about 2 years ago in both my Hondas. Not surprisingly, there was no perceptible difference in MPG (that wasn't the goal anyway). I'm considering switching from Mobil 1 to Valvoline synthetic, it's a little cheaper and some people tend to think it is better.
If anyone has opinions concerning Mobil vs Valvoline synthetic, I'd like to hear it!
I've run Mobile1 since the first oil change 40k miles ago. I think it may have taken a bit longer for the engine to break in, got awful mileage til about 14k. I live in a rural area at sea level, local mileage is about 22-interstate mileage is 24-26, if I use the cruise and not my heavy right foot.
I agree that driving habits affect the mileage more than anything....and using the AC. However, When I used Castrol Syntec I used to get some 25mpg tanks. I have used Mobil 1 the last two oil changes and I have not hit 25mpg again. I do have a few 24mpg results though.
Up here in Michigan I have to deal with gas formula blend changes as well.