First Dealer Tank sucked...

<div class='quotetop'>QUOTE(setheriah @ Mar 16 2007, 12:45 PM) [snapback]406866[/snapback]</div>

Welcome to the real world. When I bought my Prius I, too, agonized over mileage considerably less than the EPA sticker 61/55. The best I've ever obtained was in the first 600 miles when I hit 49 mpg. Then mileage continued to slip back to the mid- to hi-30s, touching 40 occasionally, depending on the weather. I also make many mile or less trips during the day and mileage can drop into the hi-20s, like you just described. Today I did a 160 mile round-trip (not a lot of miles) and it was up and down and over some of the hilliest countryside in central New York State. The average for 300 miles so far on this tank is 38.9 mpg. I still have two ticks to go on the gauge before the blinking light. Speaking as an ex-gas mileage junkie, I might suggest you simply drive the Prius, have fun in it, and be mindful that your 35.2 or 28.92827624 mpg is better than what you previously owned (I assume) and that the emission is considerably more friendly to the environment than virtually all other vehicles. (And since I also have an incurable disease, I find that life is simply too short to calculate my Prius' gas mileage to eight decimal places.) Enjoy the car, enjoy the ride, enjoy life.

 

I never come in under 40 mpg, even in the coldest, snowiest time of year. In the summer we average around 55 mpg. Your mileage will improve as the car breaks in and your driving technique improves.

As Evan says, don't try to calculate mileage based on tank fills. The bladder in the tank causes too much variation from one fill to the next.

Tom

 

Gas brand in the tank is a major factor also.

If you buy gas at discount stations like Racetrack, Circle K, Seven-11, and others. They buy alot on
the open market, so the gas blending changes from tank to tank, in ground at the station and in the
car.

I get 1 to 2 mpg more per gallon if I buy at shell, or BP.

Localy in the dfw area I have found Shell to be one of the best for my car.

 

<div class='quotetop'>QUOTE(setheriah @ Mar 16 2007, 06:04 PM) [snapback]407017[/snapback]</div>

Well, I wouldn't go quite that far. Welcome to The Guess Gauge. There is 1 thing to absolutely believe: When the last pip flashes BUY GAS.

Generally my MFD is close (1-2mpg high) to my calculation. Sometimes in the cold it is 20% high. I always believe my calculation before the MFD. However, the MFD is the only reading you have on the current tank.

I switched to Shell exclusively for the 5% rebate on their MasterCard. The changes of brand, insulation, tire pressure, and driving style have not reduced my mpg during the winter.

 

The MFD shows calculated MPG (in the US) based on the time fuel injectors are open (volume) and wheel revolutions (distance), both very small increments. Hand calculation is based on pump volume (uncompensated for temperature in the US, but volumetrically accurate to about 1/8 ounce) and odometer reading (accurate to ±0.1 mile or around 500 feet, based on standard 855 revolutions/mile tires). What neither can't account for is the energy content of the fuel. Both measures should converge over the long term.

Also, the first tank can be weird. My MFD showed more miles than my odometer.

The Prius gets better MPG than any other car currently in production. Your personal MPG will get better as the car and tires break in, as you learn to drive for fuel efficiency, and as the weather warms.

 

The Prius has a flexible bladder. You can't do hand calculations accurately. You'll have to use the screen.

A lot of short (less than 10 mile) trips aren't great.

You can improve your mileage by increasing your tire pressure.

There is also a breaking in period. Your mileage will increase with each tank. The first few are always the worst. There is also a learning curve where you learn to drive more efficiently.

 

<div class='quotetop'>QUOTE(Godiva @ Mar 17 2007, 10:10 PM) [snapback]407690[/snapback]</div>

Breaking in period? Nobody told me about that before. My 2007 hasn't ever gone below 42mpg, and I have about 3k on the car now, and the MFD says 43mpg.

Dave

 

<div class='quotetop'>QUOTE(DaveLeePrius @ Mar 17 2007, 10:32 PM) [snapback]407696[/snapback]</div>

All new cars have a breaking in period. I noticed my mileage improved after the first 2,000.

When I got mine the first tank was about 44.5 and they went up every tank after that. I get between 48 and 52 now with my tires at 42/40.

 

<div class='quotetop'>QUOTE(Godiva @ Mar 17 2007, 10:59 PM) [snapback]407709[/snapback]</div>

I think nowadays the breakin period is almost non existent, with the materials and finely tuned machinery used to create the engines these days I doubt there is much in a way of a traditional break in that we used to have years ago. It's more likely that we get used to driving the car hence the better fuel efficiency as time and mileage go up.

I completely agree with you about the hand calculations and I never understood why people put so much stock in the hand calculations when the size of the gas tank changes with temperature from fillup to fillup. Seems to me the computer would do a much better job tracking that.

Steve

 

I must be the only one whose dealer didn't short change him on fuel. In fact, they somehow put more fuel in the tank than I have since. The first pip ran out around 110 miles or so IIRC, and for my fills it usually runs out around 30 or 40mi. As a result my first tank looked really good on paper. I guess it goes both ways.

 

My dad insists on filling it up when the tank's at halfway.

How do I calculate the mileage when we're filling it up so screwy?

 

<div class='quotetop'>QUOTE(rainydysandmondys @ Mar 18 2007, 08:14 PM) [snapback]408093[/snapback]</div>

For lifetime mpg keep a record of the amount of gas pumped each time. Divide the odomoter (total miles) by total gallons.

For the mpg on the tank subtract last time's odo reading from this time's odo reading and divide by the gas pumped this time. IN THEORY, this calculation should match the MFD if you reset on each fill up.

Although I have some large deviations, the MFD's calculations are close to mine. I might actually believe the computer if it measured fuel consumption instead of sampling it.