I suppose this could work for other hybrids, but as I have an FEH I'll just recommend it for fellow owners for now.
An earlier thread asked about which gasoline brands gave the best fuel economy. The general consensus was go with national brands. I usually use Superamerica/Speedway, but last week went with gas from a Mills Fleet Farm because it was about 20 cents per gallon cheaper, and I figured any loss in FE would be small. Well, imagine my great pleasure at announcing I am, in fact, getting .5 more MPG! I know it doesn't seem like much, but nothing has changed about driving (in fact, with the heat wave I've been running the AC a bit) so I can only chalk it up to Fllet Farm gas.
No, I don't work for them or get anything for this except for more miles per tank!

 

The average MPG of part of one tank of gas is simply not enough to make that kind of assumption. If you go through a few more tanks and still see the same results then "maybe". There are just too many other factors out there....such as maybe the other stations still had 10% ethanol blends and this place has straight gasoline.

 

Actually, all stations in Minnesota are required to have E10 year round. My driving has been the same or worse over past tanks, and I haven't hit a big mileage milestone or anything. Also, this isn't a part of a tank of gas. It's the whole bloody tank. Stupid 50 mile commute.

 

Just a theory of mine, never been proven:

Gasoline probably has more energy per pound than detergents or fuel additives. Going to the cheaper gas station may mean fewer additives in the gas, but may give better MPG in the process.

You don't need detergents every tank. Maybe 3-4 times a year would clean any deposits. After all, the mom & pop stations do not own their own refineries, now do they? So their gas comes from the same source as the national chains, and it's the same gas, with the same "clean-ness" minus some additives.

P.S. note my MPG below, and I always buy the cheapest stuff I can find.

 

That makes a lot of sense. Now if I could only get 37.5!! I'm at 33.2 MPG at 2950 miles on the car, and since this is now 14MPG over my last car I'm pretty pleased. I did notice with this tank I'll get close to what the "Miles to Empty" said right after I filled up. I should make it to 450 miles and I've been getting 430. I know the little difference per gallon can't add up to this, but maybe the computer just "reads" this gas better.

 

This says it all to me. My mileage took a big jump when I got to around 3,000 on the ODO. The vehicle break-in period is a couple of thousand miles. You will notice your mileage increases no matter what kind of gas you use. I couldn't get better than about 25mpg when my MMH was new, but when I got to 3,000miles I was around 28-29mpg without changing my driving habits or routes.

 

I have noticed a similar trend with my 08 FEH AWD, just over 1000 miles.

While I've been at or around 33 MPG pretty steadily since driving off the lot, the "Miles to Empty" display will usually get near zero with about 420-430 miles on a tank, and the fuel needle will also be hovering right at/around E.

Both times I've filled up (427, 418 miles) I've only added about 12 gallons (at first "click" / auto shut-off). The NAV matches my hand calc's pretty close - to within 0.2 MPG or so - but I can't help but feel like I could be getting more "distance per tank." Obviously I'm not counting on using 15 gallons every tank, but haven't people commented that right at 0 MTE there's about 1.3 gallons left? Or, maybe to phrase that better, that at 0 MTE the max amount of fuel you can add is 13.7 gallons? (Not counting if the wheels are lower and angled to allow more gas in the tank)

I guess what I'm getting at is, does the "break-in" period help the car recognize that yes, it CAN go more than 430 miles on a single tank? It CAN push 450 and higher without being empty?

Thanks!

 

I think its just a holdback to prevent someone from running out of gas. I can see someone screaming bloody murder if they are in the boonies because they decided to drive until the tank read 0MTE and it died right then. Manufacturers are going to put a little buffer in there.

 

My car's low fuel light comes on when there are 50 MTE. This time, I ignored it and went 453.1 miles. It said I was "out of gas" at 435. I'm a chicken, so I didn't push it. I did put in a little over 13.5 gallons. When I filled up last time, it had said 475 miles to empty. This time it said 495. I think I might push it to 470. Oooh, I'm living on the edge.