This MPG problem is nuts!

[robinjoe]

Arthur,

I'm guessing that the first time (when you got the bad mileage) when you filled the tank before the trip that the tank didn't fill all the way. Sometimes the pumps kick off prematurely. Then when you filled up after the trip you filled it all the way up. This would give the impression that you used more gas than you actually did use.

The opposite was true when you got the extremely high mileage. The tank was full to the top when you started the trip. Then when you filled it at the end of the trip, the pump stopped before the tank was all the way full. This gave the impression that you burned less fuel than you actually did.

This is why you need to average you mileage over several tank fulls to get accurate results.

The best way to do it is to write down the odometer reading the next time you fill the tank. Then write down how many gallons you use for each fill-up. Do NOT reset your odometer. Then at the end of three or four fill-ups divide the total miles by the total gallons pumped since you started.

Doing it this way rather than averaging three or four individual trips is better because longer trips would be given less "weight" per mile than shorter trips between fill-up.

You can still calculate mileage for the individual trips, but always save the original odometer reading. You should probably write both the trip odometer and main odometer readings down.

Joe

[PTSleeper]

I gave up worrying about milage. I love this car and letting the horses run is worth every drop of gas it burns. That's why I bought this car. It only took 1 test drive and that was it, I had to have it. Over the past 12 years I bought a new/used car about every 1.5 years because I always got tired of what I was driving or wanted something better. Not with the GT I having as much fun now as when I drove it the first time. Worrying about the milage decreased the fun factor. One thing that might help is when you are going down the street and you see a red light up ahead immediatly lift your foot off the gas and coast to the light, within reason. Or shut the car off at long waits at lights. I look at it this way, everytime I save a little gas. That's one more time I can put my foot in it.

[Mean Green]

I have heard that it is not wise to top it off. There is a sensor that can get screwed up and it is pretty expensive to replace. As far as I've heard this is true in all new cars. I've never let them top off any of my PT's. It's also not wise to always run it below 1/4 of a tank as the fuel pump is inside the tank and is lubricated by gasoline. If you do run it below 1/4 of a tank often the fuel pump will dry out and would have to be replaced and because it is in the tank it isn't cheap.

[Gary04GT]

quote:Originally posted by taikuchin
...Not necessarily...Best way for accurate measurement is to average over several tanks full, the more the better. Not sure the shut off valve is very accurate...

Good point. This probably is the best way to calculate MPG providing you drive a good number of highway miles using several tankfuls of gas. However, I forgot to mention the [u]most important factor</u>:
I drive [8)] like a [u]professional</u>!!! [|)] [?]

[amazingarthur]

I just got back from about 600 miles of driving.

It was interstate all the way, cruise set at 75mph.

Filled up 3 times total and guess what?

I'm back at 22.3mpg.

Is there really that much of a difference between cruising at 62mph and 75mph?

Thanks for all the input.