Actual, honest, real world MPG from your 6.5

[3500GMC]

Not that any member here would pull my leg.

Let's see some numbers. Let us know your truck's config or weight.

 

[bk95td]

92 k2500 3.42 gear ratio 4l80e 245-16E tires3"-4" hearthrob exhaust, gm3 turbo. I got 18.2 on a interstate run at 80-85 mph from minneapolis to milwaukee last labor day weekend. I haven't checked it for everyday driving. My front end is slightly out of line so it could get better. I have no idea how old the injectors are. No black smoke.

 

[ak diesel driver]

Summer about 17-18 winter about 14-15. Probably gain 1-2 without the lumber rack

 

[Paveltolz]

96 K1500, 3.73 gear ratio, 4L80, 33 x 12 BF Goodrich AT, 3" suspension lift (lots o wind an rolling resistance, Heath Exhaust kit w/cross over, SSD Air Intake, S to F swapped intake manifold, 5000 mile Bosch bodied-china-gut injectors and vacuum pump w/waste gate. Ran this config over hill and dale to Heath's at 70mph and averaged 16 mpg for 500 miles except the last leg over "Cabbage Patch (6% forever) and over the Yakama Passes to Ellensburg where I got a jaw dropping 14! Haven't seen that since I installed the exhaust and was having fun on the winter blend. Dropped the stock PCM, vacuum pump, solenoids, waste gate and SSD intake for GLE, TM, AFE intake, new injectors (w/real Bosch guts) and added a 5" chrome tip to the exhaust. Got 15mpg on the return trip over Yakima pass and Cabbage Patch against a wicked head wind. 15.5 across the rest of Oregon and past Boise against same @#$%^ head wind and 16+ the rest of the way home (I credit the exhaust tip). Speed consistent with the trip out.
Prior to the upgrades, I was getting 16.5 avg with a mix of highway (55 mph+) and City. Will see how it changes after the foot settings calm down and summer blends come in to play.

 

[GM Guy]

1996 GMC C2500(HD) 6.5L 5spd 2wd, ECLB, 245/75R16s, 3.73s, completely stock (is that GM 4 turbo?), non functioning turbo, 400 miles of pure highway, 100 miles of mixed driving, 16.5 mpg, all empty bed, expanded metal tailgate. 70 mph average. eastern KS to western KS via highway 36. (mostly flat) winter time.

me driving dads 6.5L
1992 GMC C3500HD 6.5L 5spd 2wd, RC 159.5" WB Chassis Cab 4.63s, 225/70R19.5 pulling 20 ft bumper pull trailer, truck and trailer containing farm equipment, low to ground for the most part, not too much air drag 23K lbs total combination weight. during summer KS to Idaho, mainly I80. 9.5-12 mpg. stayed above 10 if parking brake wasnt on. the 9.5 mpg leg was with it on.

the 92 has no a/c, so there is less pull from no a/c.

overall these 2wd 6.5Ls impress me on mpg.

 

[540s10]

I get 18.4 average on winter fuel with a 4x4 4l80 3.73's and 300k miles. I also have no splash pan infront, a WT grill and no tailgate which worsen my economy. Only engine mods are a diamond eye exhaust and a homemade turbo master which probably isn't putting out dick for boost.

 

[WarWagon]

7.2-8.5 MPG. Uphill both ways pulling a 24' trailer. 13860 LBS total give or take cargo in trailer. 4.10 rear.

 

[daustin]

My '93 3500 DWR 2WD, 4L80, GM-8 turbo, 1/3 IP turnup, '97 round HD airbox, 3" exhaust straight-piped to rear with 4.10's gets 13-14 loaded & pulling 8500lbs dual axle trailer. Gets 16mpg unloaded not pulling.
Don

 

[Big T]

17+ on the '95 with 4.10s running at 75 mph. Slightly less than 16 on the '99 with 3.73s and ATT at 75 mph.

 

[Odlaw]

Solid 19.5 back and forth to work. Occasionally, I see 20-22. This is tank after tank over at least three years and is very well documented. I have a 34 gal tank, I normally run her down to about 6 gal. I always get 550-600 miles on roughly 28-29 gallons of fuel. Very flat down here. Haven't really had her on the road without something heavy on her back so I have no empty, hwy mileage. I also run Power Services additive (for the cetane boost) and 16 oz. of Super Tech (wally world)2 stroke oil per tank.

Towed a huge pontoon boat recently...IIRC it was about 300 miles round trip. Got right at 14 mpg running 60-65 - cruising on flat ground, steady 10 lbs of boost - that thing was like pulling a parachute!

See my sig for truck setup.

The HHO generator nets me right at 2 mpg gain.

 

[chefmike]

I am still getting mine in order, but the first couple of tanks of mixed driving have seen 16mpg. I am running stock. Hoping to open up the exhaust soon, make her happy, hopefully up the mileage!

 

[Chevylover]

Between 12.8 Liter to 20.5 Liter per 100 Kms, depending on the right foot, towing, etc.
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or for the "non-metric" people : 18.36 mpg to 11.56mpg .............





Cu,
Sven

 

[treegump]

i've been getting 13.5-15.5 empty, but I average at 15.5 when I pull or haul, no matter what the load. Probably doesn't help that my right foot is heavy. This is with 265 75 16 tires, with uncorrected gauges. I know that my speedometer is 5 mph off, so I don't know how that effects my calculations.

 

[guybb3]

21.5 on a trip to Pittsburgh last weekend. Averaging around 18, non trip mileage . Summer fuel year round and no mechanical fan right now. I forgot to add; my injectors have 161,000 miles on them (new ones not installed yet) and factory computer tune.

 

[Matt Bachand]

11/14/2009 132,169 12.939 $35.70 $2.76
11/19/2009 132,355 16.114 $45.26 $2.81 186 11.543 Sae-30
11/19/2009 132,389 3.056 $8.71 $2.85 34 11.126 Bio
11/27/2009 132,601 18.633 $51.97 $2.79 212 11.378
12/3/2009 132,810 18.550 $52.13 $2.81 209 11.267
12/08/09 132,991 16.640 $45.91 $2.76 181 10.877
12/10/09 133,113 18.340 $51.16 $2.79 122 6.652 Plow
12/15/09 133,309 18.615 $53.96 $2.90 196 10.529
12/18/09 133,450 14.070 $38.54 $2.74 141 10.021
12/21/09 133,550 15.800 $43.59 $2.76 100 6.329
12/30/09 133,709 15.487 $43.35 $2.80 159 10.267
1/2/2010 133,796 13.973 $39.39 $2.82 87 6.226
1/6/2010 133,914 15.468 $45.46 $2.94 118 7.629
1/13/2010 134,100 17.231 $51.33 $2.98 186 10.794
1/25/2010 134,335 16.606 $48.97 $2.95 235 14.152
1/29/2010 134,518 17.822 $51.84 $2.91 183 10.268
2/3/2010 134,644 12.385 $36.03 $2.91 126 10.174
2/9/2010 134,752 8.420 $24.00 $2.85 108 12.827
2/12/2010 134,882 17.019 $48.83 $2.87 130 7.639
2/18/2010 135,028 16.033 $46.00 $2.87 146 9.106
2/23/2010 135,192 14.421 $42.38 $2.94 164 11.372
2/25/2010 135,270 13.949 $41.00 $2.94 78 5.592



That was plowing season. I average around 12.8 normally. MPG are on the far right.


9500-10k w/out plow, 11,000lbs w/plow.

That one had a lot of highway. Last I checked I got around 16-17 Highway.

Also in winter, I High idle it for 10-15 minutes at least to warm it up. I also stop at the dump almost every working day and unload the debris. I of course leave it idling there too.

 

[Matt Bachand]

11/14/2009 132,169 12.939 $35.70 $2.76
11/19/2009 132,355 16.114 $45.26 $2.81 186 11.543
11/19/2009 132,389 3.056 $8.71 $2.85 34 11.126
11/27/2009 132,601 18.633 $51.97 $2.79 212 11.378
12/3/2009 132,810 18.550 $52.13 $2.81 209 11.267
12/08/09 132,991 16.640 $45.91 $2.76 181 10.877
12/10/09 133,113 18.340 $51.16 $2.79 122 6.652
12/15/09 133,309 18.615 $53.96 $2.90 196 10.529
12/18/09 133,450 14.070 $38.54 $2.74 141 10.021
12/21/09 133,550 15.800 $43.59 $2.76 100 6.329
12/30/09 133,709 15.487 $43.35 $2.80 159 10.267
1/2/2010 133,796 13.973 $39.39 $2.82 87 6.226
1/6/2010 133,914 15.468 $45.46 $2.94 118 7.629
1/13/2010 134,100 17.231 $51.33 $2.98 186 10.794
1/25/2010 134,335 16.606 $48.97 $2.95 235 14.152
1/29/2010 134,518 17.822 $51.84 $2.91 183 10.268
2/3/2010 134,644 12.385 $36.03 $2.91 126 10.174
2/9/2010 134,752 8.420 $24.00 $2.85 108 12.827
2/12/2010 134,882 17.019 $48.83 $2.87 130 7.639
2/18/2010 135,028 16.033 $46.00 $2.87 146 9.106
2/23/2010 135,192 14.421 $42.38 $2.94 164 11.372
2/25/2010 135,270 13.949 $41.00 $2.94 78 5.592
3/3/2010 135,442 14.754 $43.51 $2.95 172 11.658
3/9/2010 135,584 15.223 $45.50 $2.99 142 9.328
3/16/2010 135,719 12.153 $36.08 $2.97 135 11.108
3/20/2010 135,900 14.690 $43.91 $2.99 181 12.321


That ones to date. No plowing done in March.

You guys will see TRUE, Documented MPG Data for now VS ATT Turbo Install.

 

[DieselSlug]

I believe we are still on winter blend fuel.
I am guessing i weigh in the 7,000 pound range. (not quite sure) (w/o plow)
My speedo is 1-2 MPH off @ 55MPH.
265X75R17'S Bridgestone Duravis', Which are almost 275's due to rim size.
3.42 Gears.
4L80E.
14K on rebuilt engine.
Marine Injectors.
Boost set to 12 WOT.
Stupid gm-4....
I was getting 14.9 before i chipped it.
Now i am getting 16.8, this is all country roads small town driving. I rarely see highway.
Just this tank today i started adding Power Service Kleen Diesel, says raises cetane by 6 points. We will see about this....
I am leaving the 21st of April to go down to the outer banks of North Carolina, so that will be a major fuel mileage test.

 

[WarWagon]

You guys will see TRUE, Documented MPG Data for now VS ATT Turbo Install.

I can't wait.

Really.

I may join you in documenting this. :iamwithstupid:

 

[SmithvilleD]

My truck's configuration is in the signature for the most part. Believe weight is in the 6700# area. 245/75-16's. Fresh engine & most components related to fuel economy.

2 most significant things I've noted related to fuel economy are:

1. It will average a bit higher if mostly highway, but held to under 65 mph. Otherwise normal running w/ interstate traffic @ 75 mph seems to lower highway mileage to the point about equal to mixed city/hwy driving.

2. Swapping from 180 to 195 thermostats appears to have bumped fuel economy 1 mpg. Need longer term data to average as only a few tankfuls that way last Fall, before winter fuel & temps skew the #'s. Made the change in mid-Oct & the #'s seem to confirm their really is a bit of efficiency to be gained by holding the coolant minimum operating temp 15 degrees warmer.

Matt & I use the same spreadsheet to record this. Just write the truck's mileage on each fillup receipt & save them 'til you've got time to input the numbers. Once in the habit, it doesn't really take much time & provides good, real-world average mpg #'s.

3/24/2009 157,687 27.755 $56.50 $2.04
3/29/2009 158,201 26.843 $59.03 $2.20 514 19.148
4/8/2009 158,751 29.330 $59.51 $2.03 550 18.752
5/24/2009 159,227 25.410 $60.48 $2.38 476 18.733
6/10/2009 159,718 25.830 $62.52 $2.42 491 19.009
07/02/09 160,169 22.712 $56.76 $2.50 451 19.857
07/05/09 160,645 24.980 $64.92 $2.60 476 19.055
07/21/09 161,175 28.606 $70.63 $2.47 530 18.528
08/08/09 161,636 24.717 $64.24 $2.60 461 18.651
08/24/09 162,199 29.044 $72.00 $2.48 563 19.384
10/01/09 162,505 16.257 $39.02 $2.40 306 18.823
10/8/2009 162,710 24.804 $64.49 $2.60 205 18.505
11/13/2009 163,236 26.782 $72.31 $2.70 526 19.640
11/14/2009 163,313 3.930 $10.22 $2.60 77 19.593
11/25/2009 163,461 7.682 $19.97 $2.60 148 19.266
12/1/2009 163,820 19.349 $52.63 $2.72 359 18.554
12/31/2009 164,261 25.016 $67.54 $2.70 441 17.629
1/2/2010 164,531 15.467 $42.07 $2.72 270 17.457
2/15/2010 165,004 24.314 $60.79 $2.50 473 19.454
3/8/2010 165,497 24.837 $67.06 $2.70 493 19.849

 

[Ratman]

My truck in my signature averages 16-17 hot-footin' it around town (I don't haul anything, -I just haul butt) ):h

I'm running 285's for tires

GM-4 is wired shut, peak boost levels are around 18-24.

Non intercooled, no WMI, EGT's well below 1000 pre-turbo, runs very well. :thumbsup: