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Actual, honest, real world MPG from your 6.5

Signature rig running at 8200 lbs. toolbox loaded and fully fueled sees about 14 mpg.

She got 211 mpg towing an RV one time but we don't talk about that.
 
Well the mileage I came up with was based on a 42 gallon gas tank. If I do have the 42 gallon gas tank I get about 525-540 miles per tank full. Considering my 295's can we say I'm seeing 15 mpg if I take into account that my odometer registers less mileage due to the bigger tires?

Also how can I tell with out waiting till she's almost empty if I have a 42 gallon tank? RPO codes? Door jamb sticker? Ask the genie in a bottle or Siri on my iPhone?
 
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14 around town/mixed driving. 18-19 on the highway. Highest I ever got was 23 on a trip to Cape Cod. But that was a once in a lifetime thing.
 
6.5TD.Club said:
Well the mileage I came up with was based on a 42 gallon gas tank. If I do have the 42 gallon gas tank I get about 525-540 miles per tank full. Considering my 295's can we say I'm seeing 15 mpg if I take into account that my odometer registers less mileage due to the bigger tires?

Also how can I tell with out waiting till she's almost empty if I have a 42 gallon tank? RPO codes? Door jamb sticker? Ask the genie in a bottle or Siri on my iPhone?
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If you like, I'll calculate the % difference on your odometer and speedometer for you. Let me know what size tire your door sticker indicates, probably 245/75-16. Need to know that to know what your dash is calibrated to.

I'd bet you have a 42 gallon tank. Regardless, you can't check mpg without doing miles and gallons calculations, you can't say you went about this many miles on about this many gallons and have any sort of accuracy. Fill the tank, run through close to a full tank, even better if you run through 2 tanks. Fill the same way you filled the first time, and the gallons used and miles traveled give you the accurate mpg number.
 
Also, if at all possible, use the same station and pump. Different pumps can possibly affect the number of gallons used. I know that all pumps are supposed to be calibrated accurately, but the shut-off on the nozzle isn't going to be as accurate.

Don
 
In the morning I'll post what my stock tire size was. I always put gas at the same gas station.
Thanks all for the help with this.
 
OK, 245/75-16 revs/mile is 682. 295/75-16 revs/mile is 622. So you are going 8.8% faster than your speedo indicates, and are traveling 8.8% more miles than your odometer tells you. When your speedo says 60 you are really going 65. When your odometer says you traveled 400 miles, you really traveled 435 miles.

It's still only a bit over 1 mpg difference if you are around 14-15 mpg.
 
Okay, so if per full tank of 42 gallons if I register 530 miles I'm actually doing 576 miles per tank full. The math would be 530x8.8%=46.64 miles not registered due to my bigger tires. So I'm getting about 13.71 mpg. Wow that sucks.
 
Correct. But, as I said earlier, if you are not calculating the miles traveled divided by the gallons pumped in, full to full, you can't go by the number.

14 mpg is about what I'd expect in mixed driving in your truck. My K2500 Suburban lost about 2 mpg when I went from skinny 235/85-16's with highway tread to 265/75-16's with more aggressive A/T tread. I had 4.10 gears, your 3.73 should be a bit easier on fuel but not by all that much.
 
On most of my vehicles The 265/75R16's made the speedometer and odometers more accurate as checked by other vehicles, GPS and those flashing speed signs along the highway.

When I checked with the 265's on it matched up with all of those.

From my experience, you never really know how much fuel you are getting at the pump. I've put 6 gallons in 5 gallon cans - I'm pretty sure that 5 gallon mark on the cans is pretty accurate.

Funny thing is, I've never run across a pump that was off calibration in the customer's favor

I got rid of my gas tank several years ago and have to get gas in cans for what I use here. I end up getting road diesel in cans occasionally also. Just when I can't afford to by 500 gallons at a crack.

I wish there was a way to accurately measure the fuel you are buying, aside form pumping it into a container and then dumping it in the truck.

If you get diesel from the same pump regularly, It wouldn't hurt to fill a few 5 gallon cans to see how much you are actually getting compared to what you are paying for. Be aware that most 5 gallon cans wil hold more than 5 gallons, but most also have a mark someplace to indicate the 5 gallon level
 
Driving some hills and flat around 55 mph mine at the pump got right at 24 mpg. its a 6.5td 95 heavy half 4x4 stock with 4l80 auto 3:73 gears. its at 298,xxx miles. the truck has always got great mileage. it pulls well has been a everyday driver for a few years. in town I would guess around 18 mpg.
 
CHRIS F said:
its at 298,xxx miles. the truck has always got great mileage.
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Maybe once it's broken in the mileage will improve! :happy:

That's great mpg, the 55 mph with 3.73's is about the optimum place to drive it for max mileage. My trucks have all had 4.10's and driving at 70 plus the rpm are up over 2,300, really kills mileage at that point.
 
Pulling the camper, in 170 miles, off set for the bigger tires included, it took 15 gallons.
285/75 R 16 tires, stock was 245/75 R 16. for some reason the speedo is off only about 5%, I dont know if the kid I got it from ad it recalibrated.
Just plain old highway it is running 15 to the gallon, consistent, using same pump at the same station and setting on the same side slope each fill up.
4:10 gears and 4L80 trans.
I think that if I get over to the shop where the mech. has the OTC Genisys scanner, reset the timing, I think it will improve. I hope.
 
You are not very far off on your speedometer. I have 265/75/16 tires, one size larger than stock, and the speedometer is almost exactly on.

Don

ps-I should have added that I have 4.10 gears , and the 4L80E transmission also.
 
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