2005 Prius screen isn't accurate!!

It's not based on a full tank of gas, it's based on how much fuel goes thru the engine and the miles driven. You have a rubber bladder in the tank, in cold weather you can not fill up as much as in warm weather so judging by how much is left in the tank is innaccurate.

 

Because of the rubber bladder in the tank, filling it up takes different amounts due to the flexability of the bladder. Ergo on cold days the tank will hold less fuel than on warm days.
Question: Did you calculate your 28mpg by filling up the tank, driving 314 miles and filling up the tank again, then dividing the number of miles driven by the amount of gas it took to fill up again? If you did you had to put in over 10 gallons, with the fuel guage on two pips, that seem either unlikely or your fuel guage is not working.

 

This doesn't work at all. Just like on most other cars, the fuel gauge doesn't represent the whole tank, and the bars are not linear. And specific to the Gen2 Prius, the rubber bladder throws a major wrench of inconsistency into the calculations.

Your MPG must be determined from fillups. And because of the bladder, you will need to keep a fuel log and average together many consecutive tanks if you want an accurate figure.

 

Hard to be accurate when the tank size varies, they got rid of the rubber fuel bladder starting with the 2010 model year, so your calculations would be a little more accurate, however miles driven divided by amount of gas used will be more accurate. The display is usually optimistic by between 2 and 4 mpg high, so your 45 mpg reading shoud really be between 41 and 43. Enjoy your new ride, you'll know more about it's fuel mileage after a few tanks.

 

For your first tank of a Gen2, fill up now. Don't go below 2 bars until you know how much that takes and whether or not the bladder will cause repeatability problems.

Some Gen2 users have habitually gone well beyond the single blinking bar without any problems, but some others have run dry with a solid bar or even two solid bars. JimboPalmer, who ran out 7 miles after the last bar started blinking, espouses this rule:

When alone, fill up at one bar. Known one else needs to know that you ran out.
With the spouse in the car, fill up at two bars.
With the mother-in-law in the car, fill up at three bars. She will never let you forget being stranded.

 

I fill up at 2 pips just to be on the safe side, I think you would still have a gallon in the tank when you get to the start of one flashing pip. From where you are now, you should be able to get to 400 miles, but I would not risk it.

 

Don't wait, give us an update after today's fillup. It won't be real accurate, but it ought to be much better than 28 mpg.

 

I don't see the problem. In theory (if the gauges are accurate) then you will have used 7 gallons. What makes you think that you haven't used 7 gallons?

How many gallons did you fill it with?

 

No worries Eddie, I see what the problem is now. Yes, you're just over-estimating how much fuel was in it when you got it. When you go to fill it up you'll find that it wont take anywhere near 12 gallons, due to the rubber bladder in the tank.

Also, even in overseas models where we don't have the tank bladder and can easily put the full 12 gallons in, the fuel gauge will still show full after only about 9.5 to 10 gallons. So the bottom line is, unless you filled it yourself you just don't know if it was truly full or not. Due to vagaries of the refill volume it's best to average it over a few tanks if you want to get good MPG data.

 

Maybe, maybe not. For MPG calculations, it doesn't really count until you fill the tank yourself.

The dealer could have filled it a bit short, or sent it out on a number of test drives that burned off the top gallon before you reset the MPG display.

 

As other's have stated, the bladder will shrink when it is cold, and also stretch when it is warm. Cold temps such as what you are experiencing will also cause the mileage to suffer slightly. Based on what I am seeing so far on your fuelly report, I think you are doing Ok. To get a really good average you will have to fill the Prius several times before you can get a true average of your MPG. Click on my fuelly in my signature and study what you see there. It should give you an idea of how temperature and city vs highway will affect the MPG.

There are a lot of tips and tricks you can employ to maximize your mileage.

Take a gander at the link below and try to apply some or all of the items mentioned. It takes a while to learn how to really get good MPG on the Prius. If you apply everything, you will find that you can either meet or beat the EPA standards. Remember that your mileage will vary.

Beating the EPA - The Why’s and How to Hypermile - CleanMPG Forums

Good luck to you and enjoy your Prius.