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6.6 LMM Fuel Economy

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6.6 LMM Fuel Economy

tre55055 tre55055
New User | Posts: 3 | Joined: 10/11
Posted: 10/06/11
09:20 PM

Hey guys,

Just bought an 09 2500HD w/ Duramax. Only has 17K miles on it. ive only owned it for a week and digital screen reads 13.9mpg in the city...been nursing the throttle all week to see if it would change, but with no effect. from what ive read in threads, this seems awfully low...any thoughts?? Confused  

tre55055 tre55055
New User | Posts: 3 | Joined: 10/11
Posted: 10/06/11
09:25 PM

should also mention that the truck is 100% stock...  

kingtoid kingtoid
User | Posts: 107 | Joined: 09/10
Posted: 10/06/11
09:43 PM

the fact that it is 100% stock being the issue.  City represents a big range of stuff.  For what I would consider city driving, that's pretty good.  And I am not too knowledgeable about the BSFC of the LMM but most engines are just a bit more efficient at a slightly higher rpm than you would think.  The Cummins and VW diesels are prime examples of this.  (BSFC being Brake Specific Fuel Consumption or fuel used to make a given amount of power at a given engine speed.  The lower the better.  Also it's mainly applicable during acceleration (which is much of city driving) and towing.)

If you want that number to go up, put your DPF on the shelf for emmissions testing and hope that you don't get caught (assuming that you live in a state where that is illegal, I think that there are places where it is legal.)

For city driving the only other thing you could do is invest in a hybrid system like those from Lightning Hybrids.  This is not worth the investment unless you are going to be doing a LOT of city driving for well over 100 thousand miles.  But in that case, it is a good value.  

tre55055 tre55055
New User | Posts: 3 | Joined: 10/11
Posted: 10/06/11
09:51 PM

Thanks for the prompt response kingtoid,

ive looked into the DPF delete, im up in BC canada, where it is no problem to remove the DPF legally...only thing is it will void my warranty...i suppose i need to weigh the options...  

The_Copenhagen_Kid The_Copenhagen_Kid
User | Posts: 119 | Joined: 03/10
Posted: 10/07/11
04:46 AM

Most of the stuff that helps performance and mpg's will void the warranty. Frown Not worth it in my opinion. My trucks well outta warranty. But it's paid off too!!!  

Big trucks shouldn't be this fast!

jimmenelson jimmenelson
New User | Posts: 1 | Joined: 10/11
Posted: 10/07/11
05:35 PM

this is average for this year and engine option. There is hope though. Recommendations, shell rotella triple protection 15w40, change fuel filter regularly atleast every 20k preferred every 15k. Banks Power Ram-Air Intake System #42172. Hypertech Max Energy ECON Power Programmer $435. AMSOIL Diesel Concentrate Performance Fuel Additive. MAGNAFLOW 4" SS Turbo Back Exhaust.DPF-R GMK40 DPF/EGR Delete Kit For 07.5-10 LMM Duramax, Includes Chip and Delete Pipe Snow Performance Diesel MPG-MAX™ kit water/methanol injection 1-3 mpg increase.
Also check for software updates at the dealer for the truck. you certianly don't have to get all these at once, you should see an improvement with each item.  

kingtoid kingtoid
User | Posts: 107 | Joined: 09/10
Posted: 10/07/11
07:42 PM

I don't think that a Cold Air Intake will do that much, and not a ram air intake with city driving.  At near stock power levels the stock setup with a different filter does pretty much the same.  Manufacturers have gotten much better about intake and exhaust parts as the power levels have gone up.  Something that might help you get around the warranty issue and stick with you through whatever power you have in mind for the future, near or distant, is an EFI Live tuning system.  You can get fantastic fuel economy by adjusting the fueling, rail pressure, timing, etc., all of which EFI Live gives you complete freedom to do.  The best thing about the EFI Live tuning platform is that it gives you unlimited tunability, which means you can run your stock tune all the way up to the 4 digit power numbers with the same tuner.  And I believe that you could reload your stock tune for warranty service.  The DPF would still be a big thing, but for your situation and EFI Live license would do great things I think.  

Stygimoloch Stygimoloch
User | Posts: 127 | Joined: 11/10
Posted: 10/08/11
04:32 PM

Removing the DPF will not affect the warranty.  
1982 300D VNT
M-Pump, GT2356V VNT Hybrid turbo, A/W intercooler, W/M injection, straight pipe exhaust, W126 Gen-II 300mm brakes, battery relocated

1980 240D 3.0T
OM617.95, 4-speed

MarineOne MarineOne
Addict | Posts: 2070 | Joined: 10/08
Posted: 10/09/11
04:38 AM

With you being in Canada, double check your emissions laws to see if you can do it legally and it not affecting the warranty.

I know in the States they can void the warranty because you're removing federally mandated emissions gear and altering the ECM to make it think the stuff is still there.  For those of us in the States, you can try the Magnuson–Moss Warranty Act to get relief but keep in mind these corporations have lawyers on call for this kind of thing.

In Canada, US federal law is worthless ..... just make sure you can delete before you do it.


2006 Dodge Ram 2500 QC 5.9L - Smarty CR S-06 on SW #5

2008 Dodge Ram 3500 QC 6.7L - H&S MiniMaxx on DPF tune for towing
Titan Fuel Tank
Aero Muffler 4040XL
Nathan AirChime K3LA

Dmax_Power Dmax_Power
New User | Posts: 5 | Joined: 11/11
Posted: 11/24/11
10:53 PM

just bought my lmm. i have done mostly highway driving i have seen anywhere from 17.5 to 19.2 at 67mph. its got 3.55 in it so that probably helps as well. 'at least i think its 3.55 at 67 mph its 1700 rpm"  
cummin stroke this dmax