Originally Posted by DAC17
Although I generally haven't believed in the "premium gets higher MPG" idea, I must admit that the last two tankfuls of premium have yielded about 5% higher MPG's. I was thinking we might have gone back to summer blend gas, but maybe not.
If 5% is worth the added cost... I did some calcs, and with the added cost of premium, where I live, for the ~80 extra miles per tank (397 vs 320), it's worth it.
I did go back down to 87 for a while, but - if I recall- it's page 381 (or 351) that states "higher performance with higher octane gas) so 91 octane isn't going to kill the engine.