"Real World" diesel fuel mileage on Duramax

[WilliamBos]

Personally, I like normally asperated V8's in the trucks I buy...Nothing like a V8..My 6.2 GMC averages 16mpg in mixed driving and 20 on the highway..No fuel management either. I'm perfectly happy with it driving at least 70 miles round trip to work....I looked at a DMAX when I bought this one, just couldn't justify the 10K premium..I only tow on weekends anyway and the 6.2 does just fine for that.

Do you have to run premium in that? Considering a Max Trailer for my next truck.

 

[timswi]

Do you have to run premium in that? Considering a Max Trailer for my next truck.

Nope, runs perfect on regular..Tried a couple of tanks of premium and it made no difference in power or mileage...We don't have E85 around here though.

 

[WilliamBos]

Nope, runs perfect on regular..Tried a couple of tanks of premium and it made no difference in power or mileage...We don't have E85 around here though.

That is great! I was told that you may have to run premium if it starts to knock. No E86 here either.

 

[timswi]

That is great! I was told that you may have to run premium if it starts to knock. No E86 here either.

Never heard it knock...It does talk about that in the owners manual, but never heard a noise in over a year and 24k of miles...Most I've pulled is around 6000#, but it didn't seem to care about that one bit...I think it's good to around 9500# if memory serves without the max tow...It's a 1/2 ton 4x4 X-cab 6.5 ft bed with a 6speed and 3:42's....Nothing flat around these parts either, all hills.

The difference between this and my last similar GMC with a 5.3 and 3:73's is beyond belief..That 100 extra HP is very noticable..And I was very happy with my 5.3.

 

[jcmseven]

DeereDude, I had my local mechanic do the in-pan filter. If you have a lift or access to one it is not that hard to do. The filter is not cheap, however.

John M

 

[AKfish]

Does anyone drop the pan on the Allison and change the internal filter? I have 91000 on mine and the dealer said I should but that seems like a lot of work to me. I thought the reason for the external filter is so that doesn't have to be done.

I've got 135,000 miles on my 2003 Dmax. I've had the pan filter changed twice already - by the dealer. I also change the small, external filter every 15,000 miles per the dealer recommendation.

Most of the miles on my truck are "working" miles. Towing between Alaska and the lower 48 states with heavy loads. So, I've been extra mindful of taking care of the maintainence!

Truck averages in the 20's consistently when unloaded. Towing fuel use is so variable - I no longer pay much attention to fuel economy when loaded. :laughing:

Seriously considering a ton rig in the near future. Likely go with a SRW, though. Duals and consistent snow and ice are not an ideal combination for my purposes.

AKfish

 

[Diamondpilot]

Does anyone drop the pan on the Allison and change the internal filter? I have 91000 on mine and the dealer said I should but that seems like a lot of work to me. I thought the reason for the external filter is so that doesn't have to be done.

2002 GMC Diesel dually. Babying it pulling 17,000 camper from Florida driving 65-67, generally got 11 mph. If I really push it generally get around 10 or so. A couple tanks I got 12.25 and I was tickled. Maybe I got some good fuel for a change. Just running around empty maybe about 16-17. The best stretch for a couple tanks was a hair over 21.

Mine said external every 15,000, fluid changes at 50,000 & 100,000 dropping the pan and changing the internal at 100,000...

Chris

 

[WilliamBos]

Never heard it knock...It does talk about that in the owners manual, but never heard a noise in over a year and 24k of miles...Most I've pulled is around 6000#, but it didn't seem to care about that one bit...I think it's good to around 9500# if memory serves without the max tow...It's a 1/2 ton 4x4 X-cab 6.5 ft bed with a 6speed and 3:42's....Nothing flat around these parts either, all hills.

The difference between this and my last similar GMC with a 5.3 and 3:73's is beyond belief..That 100 extra HP is very noticable..And I was very happy with my 5.3.

That is what I am driving now, 5.3L, 3:73 and wondered how the mileage is? Can't get a 6.2L up here without tne Max trsiler, whivh is ok, as I want all wheel discs.

 

[timswi]

That is what I am driving now, 5.3L, 3:73 and wondered how the mileage is? Can't get a 6.2L up here without tne Max trsiler, whivh is ok, as I want all wheel discs.

No difference in mileage really...The 6.2 might be ever so slightly better but my 5.3 was a 2004, so there are probably new efficiencies built in..The 6 speed probably helps a bit too.

 

[WilliamBos]

No difference in mileage really...The 6.2 might be ever so slightly better but my 5.3 was a 2004, so there are probably new efficiencies built in..The 6 speed probably helps a bit too.

That is the same year as my truck. Not done with it yet, but pondering a gas HD, a 6.2 1500 CC, or go for the gusto, and get a Dmax. Will see....