Fuel Consumption Meter Accuracy?

[rroudy 98]

Anyone know what the accuracy is for the MPG the overhead console spits out. I drive 150 miles per day and have been averaging 21mpg (Via the trucks computer). Recently I wanted to see what the effect was if I didn't drive like my grandpa. The console said 18. 2, but I measured it the old fashion way by the gas pump and calculated 16. 5. Have you guys found the meter trustworthy?

 

[lmills]

Sounds like yours is reading about the same as mine. I usually find mine to be off when I calculate by hand also about the same amount

 

[Crunch]

Originally posted by rroudy 98

Anyone know what the accuracy is for the MPG the overhead console spits out.

Don't take those readings too seriously. They represent what your mileage will be if all your driving and driving conditions were identical to the slice of time when you are looking at the readout. If you never reset the console and had 30,000 miles on the truck it might be more accurate but under normal conditions it's only a guide. I can drop mine from 20MPG to 12MPG just by stomping on the pedal while driving up a hill. After I crest the hill it starts to go back up. The console reading has been both higher and lower than my hand-checked calculations. Another thing to consider is F^3 (the Foaming Fuel Factor). These trucks really let the fuel foam up the fill tube and you have to let it settle before adding more gas. I filled up yesterday (@ $1. 36/gal for those keeping track) and my calculated mileage was 15. 61, which is about 2 MPG less than previous hand-calculated values. My console hadn't been reset since I took a road trip a week before and it was reading about 19 when I pulled up to the pump. The key here is that I topped off my tank more than usual. I usually top it off with about $2 more fuel, but yesterday I waited out the foam and added about $4 more to the top-off. The disparity in those top-offs could easily account for differences in hand calculated mileage. For what it's worth, I've always exceeded the range that displays in my console when I have a full tank, usually by about 50-100 miles.

 

[JWChessell]

I have an '03 3500 HO QC Laramie 2x4 48RE LWB SRW 3. 73 RAxR, very similar to Crunch's vehicle. I picked it up in eastern Oklahoma on July 29th and drove it to the west coast. Across the flat lands of Kansas and eastern Colorado the mileage computer and my hand calculations were very close, and with pencil & paper we were getting about 20. 5 MPG at 70 MPH with no load in the bed, tailgate down (they say it doesn't matter, but I don't agree) 2 passengers and about 150 lbs of cargo in the back seat. Obviously, the mileage dropped as we started to go uphill towards the Rocky Mtns. Overall I felt that the computer gave me a fair indication of the actual mileage, and in my experience my hand calculations and the computer were usually within 1 or 1. 5 MPG of each other. Guess I'm one of the lucky ones. But after reading Crunch's post, I realize I'll have to keep a closer eye on the "foam factor" when I fill up.

 

[Steve M]

Mine has been within 1mpg in 17,004 miles. Just filled up today. 16. 6mpg city. I've quit worrying about and I've been enjoying the power.

 

[Kimber]

The one and only time I checked mine, I patiently filled to the fill neck before and after I ran about 3/4 tank. Both times I kept filling at a rate of about a quart per minute, till there was pure fuel up to the rim of the fill neck. My overhead said 19. 8mpg... hand calculated at 20. 53mpg

 

[Jim Smith]

Hey, I'm geting 15++ when towing my 5th wheel. I just love it. I've manually chercked it and it just about the same as the computer.

 

[scbroder]

I reset my overhead each time I fill up. I then compare it to hand calculations. My overhead consistently shows around 0. 5 mpg less than my hand calculations. Sometimes it shows a little higher but not usually.

I have also noticed that the harder I drive my truck the more accurate it is.

It has always been within +/- 1 mpg.

Note: most of my driving is unloaded.

 

[Dean Upson]

Mine is usually pretty close. It is the most accurate when towing.



Dean

 

[realsquash]

The first 4 tanks have been pretty much dead-on for me. The biggest variation i saw was . 3 gallons and that could just be the difference in how full I got the tank the last time I filled up.



AQ

 

[Vaughn MacKenzie]

Mine always reads 0. 5 to 1. 5 MPG low. Doesn't matter if I have the Bully Box on or not. When it was new it was almost dead-on.



Vaughn