MPG and fuel tank question

1. Not everyone is talking the same gallon size. 43 mpg in the United States is 51 mpg in the UK.
2. Within the U.S. recognize that 50 mpg is not the normal for a 2nd generation Prius. It averages 43.7 on fuelly.com and 43 among those still being reported at fueleconomy.gov. If you look at the Bell curve at fuelly you'll see that anything 50 or higher is definitely on the diminishing end of the spectrum.

Those people that get 50 or greater in the U.S only show what might be possible with the car but not what should be expected.

As for the fuel tank, yes, the bladder can be quite inconsistent. What we do is just run the car to 2 bars left on the gauge and fill it up when convenient after that point. Usually it's only 7 to 9 gallons but it's not a big deal. We're burning the same amount of gas in the car whether we fill it up today or two days from now. From what I understand, the tank has the fuel pump and/or other things in it so that 11.9 gal tank actually holds less than 11.9.

Your "miles per fillup on one bar" sounds low, though. We almost always have two or more bars at 300 miles. There are some threads here that give instructions on how to recalibrate the gas guage and it sounds like yours might be worth doing. Just make sure the car is level when you do it.

 

it's probably your driving style, what tyres pressure are you running?

 

If the two of us are both talking U.S. gallons the driving style and tire pressure wouldn't affect the 1 bar at 280 miles issue. TylerJames is getting less out of the tank than I am and he has a higher mpg.

 

Most people around here are running something in the area of 40psi front, 38 psi rear. Some a psi or two more, some a psi or two less but in that range.

 

no two bladders are created equal.

 

The higher psi means a little less rolling resistance so yes, it helps some with the mpg. With a lot of potholes I wouldn't raise them too much if you're hitting them at higher speeds. If you're going slow for them I don't think it makes much difference.

 

I am going to start by saying I have had my car less than a week, and driven it to work 4 times, so take it the way you want. I live in Colorado, and drive 31 miles each way to work. 25 is interstate. On the interstate I am between stop and go, and a max of 95 mph. When I got home today the average showed 50.2. Yesterday I was talking to a neighbor about how it was doing and it had 49.9. If I stay around 50 I would be extactic. Way better than the 25 my ecoboost Focus gets.

 

That's an important reminder. How many gallons of gasoline are you putting in your tank? If your bladder holds less gas, then your range will be lower. And how much range you get also depends on the temperature, weather, tire pressure, driving style, etc. For comparison, in the roughly 9 months I've owned my Prius, 9 of my tanks lasted less than 300 miles, 18 lasted between 300-400 miles, and 2 lasted over 400 miles.

I also would recommend stopping a fill-up when the pump stops, as long as there's more than 3 gallons pumped. Overfilling can cause problems, even if it seems like there should be more room in the tank.

 

can't say that i blame you. but many get less than that. you can see it in the fuelly signatures here.

 

tyre pressure helps a little bit, but tyre type is even more important. what brand and model?

as for filling the tank, a few recommendations are:

1) remove the cap and let it breath for a few minutes.

2) try pumping as slowly as possible.

3) try holding the pump nozzle at 45 or 90 degrees.

4) try different pumps.

 

You're running right around average for the 2007's with a large sample size. 43.7 mpg is the average as per fuelly.

Max of 95 mph and averaging 49.9 mpg? Wow, I didn't know the Prius was capable of that (from a mpg standpoint).

 

There are a few things going on here....
1) MPG is miles driven divided by gallons used; ie: Paper and Pencil and the display is NOT ACCURATE.
2) The fuel tanks do hold ~11 US gallons when new, we have never put more than ~9 gallons in ours, but have not run out nor do we plan to test it
3) DO NOT "top off" the tank, stop when it clicks off the FIRST time. The bladder can be damaged by topping off.
4) Driving style is HUGE. These cars are designed for efficiency, not rely compatible with short on-ramps and 75 MPH driving
5) There is a procedure to calibrate the fuel level sensor posted somewhere on the PC site, I found it once. It takes a while, but may improve the accuracy of the fuel gauge.
6) Tire pressure plays a role, maybe a MPG or two, not huge. The type of tire is actually commonly the more important factor with regard to tires, standard tires will never get the same MPG as LRR or ULRR tires will, even if overinflated, which is unsafe and HARSH.
7) Dragging brakes or major alignment issues also play a factor in MPG

At the end of the day, there are literally hundreds of "little things" from aero aids, pans, tires, inflation, gasoline quality, driving style and a host of others that influence MPG, especially on a 10 YO used car.