ooyahhh

I tried the Union 76 gas that doesn't have the MTBE additive and my avg mpg increased from 25.4 to 26.9. measured to identical trips from San Diego to LA.

EighTT

Interesting. I'll have to try it once my TT gets out of the shop.

TTRay

Mobil Super. My mileage is typically 23-26 MPG.
If I use AMOCO or Sunoco, I seem to consistently drop to 18-21.
The odd thing is that performance doesn't seem to suffer.

With octane ratings being equal (93), what would cause this variance?

BTW, heading home from TTE, I managed to break 30 MPG and still drove it in the 80-100MPH range for much of the way.
That hasn't been repeated though.

ooyahhh

Re: I used Mobil 91oct before Union 76

WyoTTman

I think that it is a dirty little secret

Here is the "official" line from big oil:

"Will using oxygenated gasoline hurt my gas mileage?

Only a little. Oxygenated gasoline reduces fuel economy an average of 2%-3% because oxygenates contain less energy than non-oxygenated gasoline. Many other factors, like how well your car is maintained, how you drive (do you have a heavy foot on the accelerator?), traffic congestion, rain and snow, cold weather, and tire pressure can combine to impact mileage far more than oxygenated gasoline."

Others will disagree, see

http://home.att.net/~NCSDCA/SCIENCE/poorgas.htm

My experience was about 15% reduction in fuel mpg on my Audi 4000s.