I see everyone is talking about the difference between the overhead and hand calculating your mileage. One difference might be that some people figure their fuel mileage after the have topped off their tank. I watched mine and I can add 3.9 gallons more to my tank once the pump has kicked off. I figured my mileage at that point and then also after I had topped it off. I came up with 14.4 after I topped if off. When I calculated the mileage at the cut off point I came up with 16.3 which is the same amount that my overhead was showing. How does everyone else figure their MPG?
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I don't have an overhead, but I fill up at the same pump at the same station everytime, so I figure I have to be close to the same top off point every time. So I take the fuel mileage from one fill up to the next and divide that by the number of gallons.

 

I never top off. Sometimes my overhead is only off by tenths, but usually off by about 2mpg or so. Now I never use it.

 

I have not reset the O/H since the day I got the truck.......a long time ago ... something like 4 weeks ago and about 800 miles . It is reading 15.7 to 16.1 when I look at it . My true MPG is about 13.

 

As long as you always fill to the same point (pump shut off or topped off) it will not matter.

I track all my fill-ups and have started tracking what the overhead says just for fun. Here is what I have:
Hand Overhead
Calc
14.7 14.0
16.1 15.2
16.5 14.9
13.6 13.8
16.2 17.4
17.7 16.9
17.0 16.9
15.3 16.3
15.9 15.9
14.1 15.0
15.4 n/a
15.3 15.9
13.8 14.6
15.0 n/a

 

You also have to reset the overhead each time you fill up to have accuracy.

Despite what people think, there is extensive testing that takes place to ensure the accuracy.

 

Why would one have to reset the overhead at each fillup? The gauge allegedly reads average consumption. Consumption rate has nothing to do with the amount of fuel you replace in the tank, just fuel used over a period of time.

 

The overhead is calibrated per tank.

If you drove the truck for 20000 miles never resetting the overhead and the avg. was, let's say, 18mpg.

Then you go on vacation towing your 5'er at 24000lbs GCW through the mountains. Before you leave, you top off the fuel tank.

After 300 miles of towing through the mountains at 24k lbs, you will most likely want to refuel again. Do you think the overhead will match what you "hand calculate" if you did not reset the overhead after topping the tank before you left?

Just in case, the answer is no.

However, if you had reset the overhead before you left on your trip after topping the tank, then the overhead calculation should match your hand calculation (or at least be a heck of alot closer).

 

My overhead comes in almost dead on every time. At the most it is 2/10 off but rarely. I do not top off. I have the 34 gallon tank and it seems I can not get more than 29-30 in it at fill up. But I do not like to smell like diesel so the kid pumps it. So I guess if I tried I could jam more in. But I get an average of 15-16 and thats doing 80 on highway. So the 4:10 are not helping. But she has some punch to her

 

My overhead reads pretty accurately, within .5 mpg, usually lower than hand calc. At my last fillup (about 30 minutes ago) the pump shut off at 32.92 gallons. I was able to get another 3.9 gallons in it. Streetsmoker somehow can get 40 gallons into the thing. Anyway, my overhead read 22.1, hand calc was 22.56. Close enough for me.

 

Call me crazy, but i kinda like it. liquid for of raw horsepower and torque. gas on the other hand is what you put in your four wheeler. let the kid do that one IMO

brett

 

#2 is fine, but I have many fond memories of huffing hi-test when I was a kid...

 

My overhead fluctuates from .5 to 3 mpg over actual. I reset it at every fillup. So far my worst is 12 and best is 18 actual mpg.

 

I reset mine everytime. I am on my 3rd tank with this truck and on my first 2 the overhead showed 2 MPG more than the hand calculating. I have just been doing mostly in town driving until this tank. I have driven a little more like I usually will/do with my job. This weekend I am going to meet my parents for my dad's bday and we are meeting at their house off of the lake. It is about an 1 1/2 hour drive one way so I am going to top off before I leave then when I get back to see what kind of MPG I get. It will be interstate driving the whole way. I will say though I have 1300 miles on my truck now and I show to be getting right at or around 18 so far on this tank as opposed to 16 the last 2 tanks. I still don't understand how the overhead would be so far off.

 

I reset my overhead, all functions, everytime I fill up. I have over 64,000 on the truck now. Below is what I have seen for mileage over the time I have owned the truck:

0 - 5,000 = 14 town, 17 hwy
5k - 10k = 14 town, 18 hwy
10k - 15k = 14 town, 18.5 hwy
15k - 20k = 14 town, 18.5 hwy
20k - 25k = 15 town, 18.7 hwy
25k - 30k = 15 town, 18.9 hwy
30k - 35k = 15 town, 19.2 hwy
35k - 40k = 15 town, 19.5 hwy
40k - 45k = 15 town, 19.5 hwy
45k - 50k = 15 town, 19.8 hwy
50k - 55k = 15 town, 19.8 hwy
55k - 60k = 15 town, 20.1 hwy
60k - 64k = 15 town, 20.4 hwy

It takes time for these beasts to break in. Keep a light foot and under 68 mph (under 1900 rpm) and your mileage can go up to 21 or 22 mpg.

Also, keep your engine up between 1600 and 1900 rpm for the best efficiency, even when driving in town. You can see up to 17 or 18 mpg doing about 40 - 45 in 5th going through town with my truck.