Fuel mileage

zukimaster · Jun 8, 2018

I bought a 02 Duramax a few months ago, has EFI live, 4" exhaust, cold air intake. I have never driven it more than 50 or 60 miles at a time without hauling something, but could tell it's getting good mileage, but never checked it, I had to go to Bessemer this morning, I topped it off, got on interstate, set cruise on 75, got off the exit and topped it back off, it stopped at 10.13, I squeezed 11.00 in it, that's 3.66 gallons! I put 112.1 miles on 3.66 gallons of fuel, that's 30.6 MPG! How? Am i retarded and figured it wrong?

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TacomaJD · Jun 8, 2018

Got dang, I need to buy that thing. Lol

And unless you got the computer changed to the 295 75 16 tires you got on it, wouldn't it even be a fuzz more if it's still calculating miles traveled on the odometer based on the revolutions of the 245's that came stock on it?

zukimaster · Jun 8, 2018

I got on at exit 222 and got off exit 112, and it's about a mile from where I got fuel to the interstate, so that's 111 miles for sure.

TBItoy · Jun 8, 2018

for a short interstate stint, i could see that as very plausible

I filled up my 07 LBZ in Nashville and drove to Evansville, IN and got 27+ mpg, 34" tires (speedo corrected), camper shell + 2 tool boxes in the bed.

Any mixed driving at all would drop the average to ~20 mpg.

dwa2469 · Jun 9, 2018

My 15 has a 100 horse tune efi live, deleted and all and on the interstate if I dont dog it I can easily get in the mid 20's

GONOVRIT · Jun 9, 2018

Unicorn! My 2012 Ram couldn't get 2/3's of that if it was all down hill.

kmcminn · Jun 9, 2018

Chad, how fast was you going?

zukimaster · Jun 9, 2018

70-75 easy driving

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jordan7118 · Jun 9, 2018

You wil be much more accurate over a full tank than just a couple of gallons, especially if you tend to fill past when it clicks to stop. It could be that last time you added an extra couple of gallons and that wouldn't be reflected on this fill up. Glad to see you're at least hand-calculating instead of regurgitating what the on-board miscalculates ???? love it when diesel brohs tell me their Cummins on 40s gets 25 MPG pulling a semi trailer :gtfo:

TacomaJD · Jun 9, 2018

Re: Re: Fuel mileage

jordan7118 said:
You wil be much more accurate over a full tank than just a couple of gallons, especially if you tend to fill past when it clicks to stop. It could be that last time you added an extra couple of gallons and that wouldn't be reflected on this fill up. Glad to see you're at least hand-calculating instead of regurgitating what the on-board miscalculates ???? love it when diesel brohs tell me their Cummins on 40s gets 25 MPG pulling a semi trailer

So you are saying once the fuel level hits high enough to make the pump cut off, you can still put a couple more gallons in it? Never owned a diesel, but I've always done good just to finish of the dollar I'm on in everything I've ever owned, which @ $3 a gallon for diesel per his receipt, that'd mean you are saying he could fill til pump shuts off, and continue to put $6 or more worth of fuel in it? Idk about that. Lol

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TacomaJD · Jun 9, 2018

Re:

My buddy has an 06 crew cab 4wd Duramax with LBZ engine. His normal set of wheels and tires are 35.5 Nittos on 20" Rockstars. When they go to the beach, he has a set of factory wheels and 245's he puts back on the truck and claims he gets around 30mpg on interstate, with a tune. Guess its possible at the right speed and rpm range.

Completely different side note, I was amazed at the fuel mileage that 2002 Z06 Corvette I had got. I bpught that car as a toy, but didn't realize it would get over 30 mpg's on the highway. Of course it wouldn't get **** for mileage if romping on it, but 6th gear running 75-80 and it'd be over 30 mpg. Light weight and aerodynamics at play, I just didn't expect that when I bought the car.

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Chaz · Jun 9, 2018

In my old 02 7.3 before the harpoon mod I could put in another 6-7 gallons after the pump clicked off if you can let it barely flow.

halcat · Jun 9, 2018

You could throw my truck out of an airplane at 30,000 feet and it would probably only get..say... Mid 20's before it hit the ground. But it's a ford.

zukimaster · Jun 9, 2018

After the pump clicks off, it want hold more than a gallon, or it will run out on the ground.

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onepieceatatime · Jun 9, 2018

Re: Re: Fuel mileage

halcat said:
You could throw my truck out of an airplane at 30,000 feet and it would probably only get..say... Mid 20's before it hit the ground. But it's a ford.

My 8.1 wouldn't get much over 10mpg if you threw it out of a plane.

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jordan7118 · Jun 9, 2018

TacomaJD said:
So you are saying once the fuel level hits high enough to make the pump cut off, you can still put a couple more gallons in it? Never owned a diesel, but I've always done good just to finish of the dollar I'm on in everything I've ever owned, which @ $3 a gallon for diesel per his receipt, that'd mean you are saying he could fill til pump shuts off, and continue to put $6 or more worth of fuel in it? Idk about that. Lol

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Robbiem said:
In my old 02 7.3 before the harpoon mod I could put in another 6-7 gallons after the pump clicked off if you can let it barely flow.

Every truck will be different, just like every pump may be different.

Best way to get a reasonably-accurate MPG is to fill up to the click, then drive until light comes on, then fill up to click. 100 miles or 4 gallons isn't really gonna be enough distance or fuel for a good average.

onepieceatatime · Jun 10, 2018

Re: Re: Fuel mileage

jordan7118 said:
Every truck will be different, just like every pump may be different.

Best way to get a reasonably-accurate MPG is to fill up to the click, then drive until light comes on, then fill up to click. 100 miles or 4 gallons isn't really gonna be enough distance or fuel for a good average.

I don't know if it's the same for diesels but I only ever fill gas vehicles up till the pump clicks. Always heard that when you keep trying to top them off it's bad for the EVAP system? :dunno:

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onepieceatatime · Jun 10, 2018

Re: Re: Fuel mileage

jordan7118 said:
Every truck will be different, just like every pump may be different.

Best way to get a reasonably-accurate MPG is to fill up to the click, then drive until light comes on, then fill up to click. 100 miles or 4 gallons isn't really gonna be enough distance or fuel for a good average.

I don't know if it's the same for diesels but I only ever fill gas vehicles up till the pump clicks. Always heard that when you keep trying to top them off it's bad for the EVAP system? :dunno:

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civicmindedex79 · Jun 11, 2018

Like said before a whole tank would be a better number but if this is a two-wheel drive truck and running on decently flat interstate no stop and go, I can totally believe 25-27 mpg. It is amazing what a tune and letting it breathe a little better will do for a diesel. These trucks are so bottled up trying to make them .gov friendly it is unreal.

I know its not the same but look at the TDI cars. They are getting 50 mpg pretty regular.

jeeptj99 · Jun 11, 2018

I know that once the pump clicks on my truck if i wait just a minute or two i can usually get 3-4 more in it. My thought was it was just the foam taking up area in the tank.