Easy question - MPG

When I fill up with gas near my house, and reset the mpg meter, I can get readings in the 55 mpg range as I drive back to the house - but that's less than three miles, at maybe 45 mph tops - sometimes shorter and slower depending on which gas station I go to. It will settle back down on the next few "real" trips, towards my long-term average of about 44.4 mpg.

I find that I usually get the most mpg in the fall - something about summer-formula gas and cooler, but not cold, weather seems to do the trick.

I have data on mine for about 18.5 years and about 5,000 gallons of gas. Over all that time, the MPG meter on the touch screen averages 1.03%-1.09% over what I calculate via the gas station pump reading and the odometer.

The slight spread comes from calculating against the main odometer, which doesn't have tenths of miles, and the trip odometer, which does.

Another piece of this puzzle is that I am fairly good at this point at getting the car full of gas - but, like, FULL. I can usually get another 0.75 to 1 gallon into it after the gas station pump nozzle clicks off the first time. I have only screwed this up one time, when I got a "gas in my lungs" code shortly after I fueled up. I cleared the code and kept driving and it never came back.

Yet another piece of the puzzle is gas with bourbon in it. I think if the pump says "E10" (10% ethanol) it's at least E15 in reality, and that was happening years before the recent "official" E15 authorization. You should be able to get E0, 100% gasoline in Texas if you shop around a little; if you don't mind the price premium, try a few tanks of that and I suspect you'll be pleasantly surprised.

 

Just for the record: we went up that dang hill more times than I care to count. One time was totally futile too: up the hill, down the hill, with no grandkid accumlation. Then we got a call from the other: aren't you going to pick me up? So back up we went. Finally, a short drive in the rain to a movie last night, and I think it's now sitting at 4.9.

 

Here's a thread from our friends at CleanMPG. Wayne is pretty OCD on driving a vehicle at a set speed for a long time to get a fuel economy value at various speeds, for a bunch of different vehicles over the years. I couldn't find one of the earlier Prius, but the trend of all the charts for various vehicles is pretty consistent.
Steady State Speed vs Fuel Economy results | CleanMPG