6.7L Cummins Forum

I am looking to see what some of you have done to improve you gas mileage on the 6.7. Any suggestions to improve with aftermarket parts (cold air intake, etc.) that will not void the warranty. What fuel additives are you adding (if any)? Which fuel additives do you belive work the best? I add fuel additive everyother tank and average unloaded highway around 19mpg. With out the additive I average around 14-17 mpg. This is a Tow truck so with the added weight of the wrecker unit, thats great gas mileage. Suggestions?

The truth is since these engines are so new there's not much on the market yet so I'm going to wait until after the break in period before deciding on a programmer. Hopefully by then there will be some matched packages out there like Banks has for the 5.9L Cummins (24-valve), '03-07 - PowerPack® system it just seems to me that a system matched and tested together makes more sense then different components from different manufacturers.

By the way, Welcome to the site.

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2007.5 Dodge Ram 3500 HD,QC, 6.7L Cummins, 6speed Auto, 4X4, Bighorn Edition.
Click for installs: Carr Steps PML Diff Cover Edge Juice with Attitude Volant Intake Hankook ATM RF10

I have found that my mod's have done little to improve fuel economy. They do though, greatly improved the performance. The more miles I get on my truck, the more my mpg improves. Your mpg sounds very good, what additive are you using?

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7.5 3500QC 6.7CTD 68RFE Build date June 2007
Superchips tuner 3808, Boost/EGT Laser Gauge, Airaid cold intake

I use the PowerService (silver bottle) and I would say I average 1 to 1.5 MPG better with it. I do have a lot of variables on my daily drives, but I also hand calculate the MPG and document every fillup in an Excel Spreadsheet so I'm not just shooting from the hip here.

I was hesitant to run any additive with the 6.7, but I got a personal email from the good folks at PowerService that explained in detail why they're product would work for the 6.7 and why it won't void a warranty as some think.

Guys, please don't flame me for using "snake oil" as some people call this stuff. It's a choice we can make and for me, it's simple, I see results.

I wish I got paid (or at least a product discount) for endorsements...

I started using Howes and have seen a improvement in mpg. Have you heard of it? It is formulated for ultra low sulfer fuel.

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7.5 3500QC 6.7CTD 68RFE Build date June 2007
Superchips tuner 3808, Boost/EGT Laser Gauge, Airaid cold intake

Well guys, here's my experience with using fuel additives in 3 Cummins RAMS, a 1999 (bought used with 45k) 2004.5 (purchased new) & current 07.5 (purchased new) With the first two I used additives religiously, meaning almost every fillup and with great benefit, ie. improved mileage & performance. It was very handy when I had picked up some lousy fuel on the road, indicated very quickly by the overhead. I only use the overhead for baseline readings, I have a digital fuel monitor that came with my aux. fuel tank for capturing actual fuel use. I started the same process with my 07.5, not getting any real improvements and within 35k miles, mostly highway @ 75 m.p.h. I was getting EGR codes, poor performance and lousy fuel mileage. This was before all the flashes & EGR problems started showing up. They cleaned the EGR which was full of soot & a gummy substance which required a "special" Chrysler cleaning soap. I continued using additives and the EGR clogged up two more times within less than 20k miles. I was advised by DC to NOT use any additives. I agreed to not use them and have not had an EGR code since. Truck is up to date with the flashes except for the last one - AX I believe. I used the Power Service additives mostly and sometimes the Howes as they were the most available. My reason for using additives with the 07.5 was the lubricity/cetane levels of ULSD bought on the road. So far so good without additives with 110k miles on the clock. What turned my mind concerning additives was a very exhaustive & specific lab report testing all the major fuel additives. The report is floating around on these sites - I don't have a link to it. Power Service & Howes were in the bottom 3rd as far as effectiveness AND both were putting in foreign materials that could possibly cause harm in the long run, either to fuel components or the NOX filter/DPF filter. That sealed it for me, as you can see I pile the mileage up on these trucks pretty fast and I don't need to be wasting time in the shop or paying for expensive repairs due to additives. I don't say snake oil since I have enjoyed the benefits of fuel additives in my two previous trucks. But for me, additives in the 07.5 is a NO NO.

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07.5/6.7l, Metalic Silver, 3500 fully loaded Laramie, DRW, TransferFlow 98 gal. in bed aux. tank, PullRite Super 5th wheel, AMP Research Power Steps, Firestone Ride-Right dual control air bags, Bilsteins all the way around.

I'd like to read that report. Any idea about who published it??

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7.5 3500QC 6.7CTD 68RFE Build date June 2007
Superchips tuner 3808, Boost/EGT Laser Gauge, Airaid cold intake

Here is one study where Power Service & Howes are in the middle of the pack. There's another report which goes into much more detail but I can't find it yet.
Lubricity Additive Study Results - Diesel Place

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07.5/6.7l, Metalic Silver, 3500 fully loaded Laramie, DRW, TransferFlow 98 gal. in bed aux. tank, PullRite Super 5th wheel, AMP Research Power Steps, Firestone Ride-Right dual control air bags, Bilsteins all the way around.

Nice report...Test were done on virgin diesel fuel with no lubricity additives. What happens when you do the same test on normal diesel fuel?? Is the improvement accelerated? Also, doesn't higher cetane mean cleaner combustion? If so, does that also mean lower diesel particulates? Lower particulates also mean fewer regens, less effect on egr and higher mpg. I'm not sold on the idea that additives are not good for the 6.7. I'm open to any extra data that's out there. I've found, by imperial methods, big differences in diesel fuel in terms of mpg and regen frequencies from brand to brand and I would expect that the lubricity varies as well.
I think that I'll keep studing this matter and any additional information is greatly appricated.

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7.5 3500QC 6.7CTD 68RFE Build date June 2007
Superchips tuner 3808, Boost/EGT Laser Gauge, Airaid cold intake

Found the following information while
Cetane
Cetane number is one of the most widely-known parameters of diesel fuel. Awareness doesn't always mean understanding, and there is a danger that cetane number can be confused with cetane index. A brief explanation is in order.
A diesel engine is a compression-ignition engine. The fuel is ignited by the high-temperature, high-pressure air created in the cylinder as the piston nears the end of the compression stroke. Fuel in gasoline engines is ignited by a spark plug.
The cetane number is a measure of the ease with which diesel fuel is ignited during the compression stroke. The number is determined using a specified laboratory test engine. The cetane index, on the other hand, is calculated using an equation involving the API gravity (density) and the distillation curve of the fuel. Consequently the cetane index cannot be increased and improved by cetane-improving additives because the equation doesn't account for the amount of cetane-improving additive in the fuel. If there is nowhere to put the additive into the equation, there is no way to change the cetane index except by changing API gravity or distillation.
When injected into the combustion chamber of the cylinder, fuel must quickly mix with air then ignite with no other ignition source. The time between the beginning of fuel injection and the start of combustion is called "ignition delay." Higher cetane number fuels result in shorter ignition delay, providing improved combustion, lower combustion noise, easier cold starting, faster warm-up, less white smoke, and, in many engines, reduction of some emissions. Society of Automotive Engineers publications have reported better fuel economy and increased power as a result of increasing the cetane number with additives.
When a diesel engine was run with naturally high-cetane fuel instead of the naturally low-cetane fuel improved to the same cetane number with additives, Texaco's research demonstrated an average 4.6 percent decrease in power, with an average 4.2 percent increase in fuel consumption.
The disadvantage of natural high cetane fuel compared to "additive-improved" cetane fuel is that the former is generally less dense.[/B] This lower density, as with winterized fuel, means lower volumetric energy content, so fuel economy and power per volume of fuel is reduced. Since fuel is bought by volume, this is a direct economic loss to the customer.
The NCWM analyzed data for more than 300 diesel fuel samples. Their average cetane number was approximately 44. This is probably representative of all U.S. diesel fuels. An increase of three points in cetane number above average (an increase of seven points above the minimum ASTM specification of 40) will provide added performance in some engines.
The Engine Manufacturers Association, the American Trucking Association, the American Automobile Manufacturers Association, and the recently-announced automotive manufacturers' World-Wide Fuel Charter all stress that the cetane number for premium diesel should be well above the national average. They feel that diesel engines operate better on fuels with cetane numbers above 50.

Also, here is the standard...
Premium Diesel Fuel
National Council on Weights and Measures (NCWM) approved a Premium Diesel Fuel Specification effective Jan. 1, 2004
· Cetane Number (47 minimum)
· Low Temperature Operability
· Thermal Stability
· Lubricity (520 HFRR)
Note, a refiner or distributor can call it premium if the fuel meets 2 of the 5 above….So, if you buy the fuel in summer months, you have the potential of only getting one.

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7.5 3500QC 6.7CTD 68RFE Build date June 2007
Superchips tuner 3808, Boost/EGT Laser Gauge, Airaid cold intake