Oh how I wish I drove a couple hundred miles a day so we could get an answer to this sooner... but this is my husband's commuter car... and his commute is 11-12 miles each way... then I use the car for errands as much as possible. We aren't racking up the milleage very quickly.

The little electronic guage continutes to tell us we are doing 35.7-9... which is what gave us the 38 mpg tank... but it was unnerving to see the needle plummet. So far though, the car is registering almost exactly the about of miles per tank on the predictor that we saw before... so hopefully in a couple weeks we'll have an answer.

We've been getting our gas at Chevron because it is on the Tier 1 list, but I will keep my eyes open for nearby Shell stations.

Oddly, our first tank was high octane... and we actually "seemed" to get better MPG... but it is also possible (actually probable) that the dealership topped off as much as possible... and that I got an early shut off on my last tank.

What was odd was that the dealership emphasized to us that the Altima hybrid was designed for high octane gasoline... but the manual obviously says otherwise.