New Here...and I have a few concerns...

welcome to priuschat! two things come to mind, your gas tank has a bladder, so the gauge is not very accurate. you won't know mpg's until you fill it a few times and average them out. second, you don't know how full it was because you didn't fill it. give it some time before you decide whether you have a problem. all the best!

 

Average over several tanks. Also, it takes a while sometimes to relearn driving for the Prius to get the best mpg. Tires can be a factor in low mpg, as well as a weak 12V. But at this point just drive, enjoy, and take notes on the gallons and miles for a while. Congrats and enjoy.

 

This raises a question.

For years, I determined my MPG by measuring how much gas it took to fill the tank (top off) and doing the math on miles traveled divided by gallons since the last fill-up.

When you fill the tank on a Prius, are you ALWAYS filling it to "capacity" (meaning you burned what was put in) or does it keep varying because of this bladder thing?

Also, why the "bladder?" Is it like a well's pressure tank that uses a pressurized air bladder to apply X psi on the water stored in it so the car doesn't need a fuel pump?

 

If everything turned out to be normal and you don't have LRR tires, your mpg is probably normal for a gen 2 PRius. My friend's 2004 yields about the same mpg and he doesn't use LRR tires.

 

It will vary due to the bladder, outside temp alters the size of your tank. I recommend fuelly.com and pay more attention to your average than any one tank. (you can see the kind of stats it provide by clicking my MPG below.

The bladder helps prevent evaporation of the gas. You often see clear fumes while filling other cars tank. Sadly, it is not convenient for owners, so Toyota dropped it in Gen 3.

 

So it's a non-issue for Gen3 owners?

 

...yes as Jim said above any given tank may be high or low MPG...this was always the case, but magnified with the bladder tank. You just need to average your tanks.

It would be my understanding that the new solid tanks also recover the evaporative emissions without the need for a bladder.

 

Yes non-issue Gen3 is fixed volume tank. Gen2 in USA has the "guess" tank bladder type.

 

Thanks!

 

correct. No bladder in 2010 & later.

To the OP, many factors play into it, but your 2004 will give you great mpg as you learn to drive it and maybe correct a few things. What is the tire pressure? What tires are on it? Give it some time and report back. And welcome!