hello

Jelly Bean:

You didn't get the tank full, so you were assuming less gas than you actually burned, which equates to more miles per gallon. (Fewer gallons for the miles.)

In this case, the problem was you didn't fill the tank as full as it had been. (The assertion that dealers don't fill the tank all the way is unjustified: every dealer will be different.)

But in general, that pesky gas bladder will assure that you seldom get the same amount of gas into the tank twice. That means your mpg calculation for any given tankful will be extremely unreliable. However, if you faithfully record the amount of gas you pump every time you fill up, then over the long term you'll have an accurate figure, providing you correct for any error in your odometer. (Check it against the mile markers on the highway. Those are probably surveyed very accurately.)

The bladder is not all bad, however: It prevents fumes from escaping. Fumes are pollution. And therefore gets the car its PZEV rating. It also prevents air from entering, and thereby greatly reduces the amount of water condensation in the gas.

I don't track my mileage. I am constitutionally incapable of remembering to write down how much gas I pumped. Besides, with my many short trips I'd have an embarrasingly-low number.

P.S. When my Prius was new I generally got 6.5 gallons in when the last pip blinked. You didn't wait for the blink so your 6 gallons sounds about right. The bladder seems to stretch with time, and with warmer weather, and you get more in.

 

Welcome to the mysteries of the "guess gauge". In theory it is an 11.9 gallon tank and 10 pips on the gauge for 1.2 gallons/pip. Since there is a bladder inside the 11.9 gallon tank the capacity has to be somewhat less. When fueling set the nozzle on the slowest speed and stop at the automatic shutoff. The gauge does not instantly return to full. I haven't timed it but it seems to take a minute or so. I have never not had all the pips on a fill up.

I would go to the gas station and pump what will probably be an embassaring small quantity of gas into the tank to fill it up. (Presuming you've gone at least 50 miles.) If the gauge still does not show all the pips I would have the dealer recalibrate the gauge. You could do it yourself but the procedure sounds like a PITA as you have to level the car then go through a list of gyrations.

On your normal commute (or familiar routes) don't worry about the size of the tank and fill up at 1 pip. I use the displayed miles and mpg to estimate the amount of gas used.

<div class='quotetop'>QUOTE(TNJellyBean @ Dec 30 2006, 05:15 PM) [snapback]368708[/snapback]</div>