I got the trucl last october and I've notice that sometimes I can go 260 miles gallons on a tank and other times I go a little ways past 200 miles before the check gauge light comes on. what the hell is going on here? is my gauge off? when I got about 260 miles on it i'm getting 14 mpg which is what it says it gets on paper........

 

It's weird. My MPG fluctuates a lot!!
check it:

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It makes absolutely no sense, as I drive the same way and route to work and back every day.

 

Ive been getting a solid 16 mpg over the winter, since i put on 285's ive got 15.

 

I GET THIS TOO. I GET LIKE 22 ONE TANK THEN 14 THE NEXT WTFF

 

It would be very hard to make sure that the tank is always filled to the exact same amount each time you re-fuel. If the pump stops a little early milage for that tank would seem to be higher. If you get a little extra in when you fill up your milage for that tank would seem to be lower.

Tracking my mileage I've noticed that even small differences in "full" can make large differences in the calculated mileage for the tank.

250miles on 14gal = 17.8mpg
250miles on 13gal = 19.2mpg
250miels on 12gal = 20.8mpg

So based on kiltro's graph, it would take less than a 2gal difference in fuel would make the difference from his highest to lowest calculated milage. Which means if the pump shut off a little early one time, and ran a little longer the next it could account for that.

Also, I'm a pilot and I know in our planes at work the fuel will expand and contract a noticeable amount based on temperature, so a full tank when it's cold out will actually be more fuel than when it's warm out.

Perhaps something else is also going on here, just my $0.02 worth.

 

redbaron,
that makes sense, but a 2 gallon difference in pump cutoffs seems kind of high.

 

Probably, just a thought. It could account for -some- of the fluctuation. Wouldn't the temperature play a role in fuel mileage? Colder air = more dense -> more fuel to maintain proper ratio? Or would the slight increase in power output cancel the effect?

 

the increase in power wouldn't cancel the effect. It would just be a result of the temperature issue as you explained it.
But I see your point, there has to be multiple variables playing a part in this.
I think the only way to have a better view of the whole picture would be to get a scan gauge or something similar.

 

I used to average 19mpg but that dropped to 16mpg with larger tires, 15mpg throughout the winter. I usually fill up at 260 miles which is about when the fuel light comes on but today I noticed the fuel light was on at 190 miles...
WTF where did all that gas go? 9mpg
The gas cap was locked and I have been driving normally, the truck is running great.

 

The increase in ethanol in gasoline is causing a reduction in MPG, 10% of ethanol is reported to have almost a 10% decrease in gas mileage. Not to mention it can have harmful affects on older engines, and engines not designed to use ethanol.

Support your local gas stations that still offer pure gasoline!

http://pure-gas.org/




http://www.thepetitionsite.com/1/keep-pure-gas/

 

Thanks for the link. It's time for a fill-up and I see 2 in my area.

 

290 miles driven
18 gallons pumped how big is our tank

 

Mine changed too but like said before it depends on the gallons you get.

 

I know the local news here catches a few stations a year playing with the computer that control the readings on the pumps, I must of been riding on fumes one day because I almost got 18 gallons in my tank and my low fuel light just came on. I though they go 17 gallons???

 

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My truck came with 255/75-16, but now I have 265's. How much would that throw my odometer off? Im getting about 14 mpg now. Whatever there putting in the gas now makes both my truck and car smell...guess its the ethanol?