DC should not even put these things in their trucks if they are going to be this inaccurate. On the highway it says I am averaging 19.5, but by hand it is 16.8. Then, for 50/50 driving from house to work and back the overhead claims 17.5, but actual is usually around 15.5 to 16.0. What a joke!

Just had to vent...is everyone's this bad?

TM

 

When i take long trips and average 19ish my overhead displays 26!!! Mine usually wouldn't be that bad, except for I have a little fueling box called the XZT which messes up my throttle position.

 

It`s displaying the current average. Not the overall average.

 

Actually it is displaying the overall average since it was last reset.

Sometimes mine is dead on and sometimes it is about 2mpg high. Once I turn my box on I never rely on it because fueling boxes tend to mess with the reading...

 

Mine usually reads about 2mpg high. I only use it to help keep my foot out of it! And, I only use it as a 'delta' measurement. i.e. if I can keep the MPG number higher I am getting better economy.

I would like it to be accurate, but sometimes you havet o take what you can get.

Tony

 

They are a bit misleading though when you are test driving the truck. Seems like false advertising if you ask me.

 

I think that no matter what kind of vehicle it's on, none are accurate. My wife's Lexus SUV has one. I hand calculated the mpg once, the computer said 24 something, and my figure came out to be just over 20.

Mine always shows 2-3 mpg higher than my hand calculations.

 

My 03 was dead on as long as I did not have a fueling box turned on.

 

mine was saying 9-10mpg around town and i calculated 12-13mpg

 

The only one I've seen that comes really close is my bud's '03 Vette. It's within .2 of hand calc.

 

I hand calculate my fuel usage. I have fuel records since I bought the truck with 25 miles on it. It now has 60k and I get ~16/17+/- in town, ~18/24+/- on the highway at 75 MPH and ~11.5 towing 11K at 70 MPH. The overhead has never even been even close nor do I care, nor do I care whether my assumption to correctness of the overhead display is accurate or not. If you are going to worry over a few MPG here and there maybe you need to buy a KIA. The issue of whether the overhead is a current average or overall average of fuel use is just not relevant to me. My motto is - drive it like you stole it and if I stole it I would not be looking at the overhead fuel display to see how I was doing on my current or overall fuel mileage.

 

Why do you keep so much documentation on your fuel consumption then?

 

I find if I reset mine at every fillup, its usually .04 low. If I let it got for a couple of months, its usually about 19.8 on the overhead.

 

If you do your hand calculations when the pump shuts off then your overhead will be a lot more acurate. Topping of the extra 1-3 gal after the pump shuts off is when you get way differnt readings from your overhead.

 

I keep track of the fuel for tax/farm use reasons. I found it easier to just take the reciepts, write what the mileage was on it, and give them to the wife and she logs it in a record book. Mostly, out of habit but also to take advantage of some tax/farm/business deductions. Otherwise I would not be keeping track.