GMC compared to Chevy DMax compare?

[N0DIH]

Bear with me.....A friend of mine has 2 friends with DMax's, on a GMC and one a Chevy.

The Chevy gets 18-19 mpg highway daily.
The GMC has never got over 15 ever.

He wonders if the stock calibration on them has any differences. I say all things being the same (engine/trans/gearing/body style/gearing), no.

But he was wondering if anyone has done a compare. I asked him to get me VIN's so I can compare what GM says.

One has done an exhaust swap and CAI (Banks I think), and mpg has sunk lower.
The other, exhaust only and it has dropped off some too.

Thoughts?

Thanks!

[ScarabEpic22]

What years? That might be the sign there...

[horsehaulin]

one might have 4.10 running gears, that will greatly reduce the economy. But I noticed my MPG increased after towing a nice heavy load a few times. I was only getting 16 MPG best, I have been at 18.4 for quite a while now. Thats a mix of city/highway/ricer beatdowns.

Tony

[N0DIH]

Confirmed one is a 2005. Checking on the other still... I have the actual VIN of one.

one might have 4.10 running gears, that will greatly reduce the economy. But I noticed my MPG increased after towing a nice heavy load a few times. I was only getting 16 MPG best, I have been at 18.4 for quite a while now. Thats a mix of city/highway/ricer beatdowns.

Tony

Didn't all DMax's come with 3.73's stock?

[McRat]

All 3.73's.

Our GMC's get the following highway mileage:

2004.5 LLY - 19mpg unladen 3500SRW
2005 LLY 23mpg unladen 2500HD, modified engine
2006 LBZ - 20mpg unladen 2500HD

All three are tuned with EFILive.

[Lennart]

All 3.73's.

Our GMC's get the following highway mileage:

2004.5 LLY - 19mpg unladen 3500SRW
2005 LLY 23mpg unladen 2500HD, modified engine
2006 LBZ - 20mpg unladen 2500HD

All three are tuned with EFILive.

That is on the trailer, right?!

[yellowC6ohio]

alot of it has to do with driving style. i'm getting 10 more MPG out of my cavalier by shifting at 2000.

[Brian1]

Well from all the reading if both trucks have the same same year, OS tune, same cab and bed setup, Same drivetrain gears. Basically identical other than brand name and even they cam off the one after the other on the same day on the same line. Then driving exactly the same side by side one will more than likely have better mileage than the other. Why exactly I don;t know but that is just the way I see it related to many post like this on other forums.

Brian

[duramaximizer]

FWIW The newer 08+ duramax's can be gotten with 4.10's.

Both have 3.73's I am betting.

The newer one gets the better mileage would be my guess, that 2005 lly needs the turbo intake horn modified.


http://www.duramaxdiesels.com/forum/...ight=killerbee

[horsehaulin]

Actually the LB7 needs the intake horn modified and the LLY needs either a LBZ or Kodiak mouth piece.

The LB7 has a restricting intake horn, while the LLY has a restricting MP. Once either is fixed the trucks will run exceptionally better. I got .5 MPG better by modding the intake.