The other day I got gas and they put regular, I stopped them at about 10gal and told them to put the rest premium.

Today on my ride home I noticed a full +1 improvement in mpg. I cruise control driving home, and everything else being equal, AC off, windows closed. Not saying I will continue to do this as I know its not good for the car, but just thought I'd share.

I know the ecu adapts so I'm guessing maybe it just got confused? Does that make sense?

I would just guess driving pattern.

I'm just confused as to where there are still full service gas stations? That is crazy!

I would totally agree. The higher octane means the gas is less prone to detonation. So in a sense since you realize that regular gas was put in your lead foot lost a few pounds.

Well thats the thing, I use cruise control id say about 90% of the drive home, 74mph same as any other day.

i fully expect to get like 7mpg on the ride to work tomorrow just so it'll even out, lol

per state law, NJ only has full service gas stations.

Technically, lower octane requires less energy to ignite (higher detonation propensity) and is therefore more fuel efficient. I'm not sure if it's enough to be noticeable but it is possible.

If you were driving in such a way that the ignition timing was not being retarded, then its possible that you would get better gas mileage.

it depends on the gas. If they use ethanol to raise Octane, then there is less energy in the premium fuel = worse mileage.

Learn something new everyday. Thanks

You've seriously never been to jersey?
Did you know that dont have left turns there on major state roads?