DPF - WTF?

New Diesel Trucks

Posted March 28 2008 03:58 PM by FeatureEditor
Filed under: Diesel Trucks, Tech Tips, Diesel Observations, Trend Observations

It's amazing. The new diesel trucks with the 6.7L Cummins, the Duramax LMM, and the 6.4L Power Stroke with compound turbos have significantly lower emissions than the engines they replaced (5.9L Cummins, Duramax LBZ, and 6.0L Power Stroke). In addition to pumping out less NOX and CO2, the new trucks put out 97 percent less soot. Amazing, huh?

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That dramatic drop in the amount of grime escaping the tailpipe comes with a price, though. To become nearly soot-free, the new diesel engines have to rely on diesel particulate filters that trap unburned particles inside a porous catalyst. Soot that does not immediately cook off becomes stuck in the filter, where it's stored until the engine computer senses enough backpressure and decides it's time for a burn-off called a regeneration cycle.

That "regen" can include extra fuel being dumped into the cylinders after the combustion cycle in order to heat up the DPF. Since that fuel is being used to create heat, and not horsepower, it can't be helping the fuel economy.

We'd like to hear from new truck owners who are dealing with DPF trucks on a daily basis. Are you experiencing poor fuel economy? Does the truck constantly go into "regen" mode? Has your DPF ever become so clogged that you got a "Check Engine" light and had to go back to the dealer? Or, has everything been hunky-dory with your new clean-diesel truck?

Post your comments below and make sure to let us know the make and model of your truck along with any upgrades you've added.

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Reader Comments:

1. I own a '07 3500 megacab 4x4 dually. Which averages 16-19mpg. A few weeks ago I scheduled a routine service along with a spray in bed liner. I was given a '08 f450 superduty dually as a loner. I drove the truck over the weekend. I averaged 8-10 mpg driving very conservatively. Even driving 5mph under speed limit. I was in awe. I actually considered buying this truck until I drove it. That experience made me an even prouder Dodge owner. Come to find out, the f450 was traded for a megacab because of fuel economy.

S.M_0_K.M - Posted April 1 2008 12:18 PM

2. i own a 07.5 megacab with 7,000mi on it havent had the dpf indicator come on once i am getting 19.5 mpg at 60mph i think thats ok my buddy bought a 08 7.5 crewcab it has 5,000mi had to take it in for dpf issues after that he has had the regen prosses happen twice i dont get it.

baddodges - Posted April 2 2008 04:12 PM

3. i own a 07 4 door 2500 4x4 and have 3600 miles on it ,have never had any alerts or regens,but i have never gotton 15 mpg about 14 to 14.5 is every tank,it makes me sick i exspected about 19 but i do keep my foot in it alot and come on guys u know its hard not to turn the monster loose,i do plan on removing the dpf and others in that section of pipe and replacing with strait pipe been talking to other owners that done it with gains and no pains

worthog - Posted April 6 2008 09:57 AM

4. i drive a dodge 3500 4x4 6spd flat bed with 25k on it and the highest mileage i have seen on it is 13mpg it avrages 11mpg thought i hate the fuel milage i am buying the dpf delete pipe and wiring for the truck to get rid of it to try to get better milage, the truck is always in regen mode and its been to the dealer ship with problem of having the foot to the floor and no power then all of a sudden it gets all the power in the world slams you in the seat and blows a cloud of smoke like you wouldnt belive.

crazycooter460 - Posted April 7 2008 07:38 AM

5. Having a 5.9 I find it hard to understand why dodge whent to the 6.7 while rising fuel costs persist. I get between 22-24 mpg 3500 mga cab.
Go back to 5.9 decrease noise and exhoust and you got a winner. Ford and GM use more fuel.

lehbk - Posted April 30 2008 05:41 PM

6. If anybody out there knows a proven way to get the filter and cat out of the exhaust please let me know as i am tired of the bad mileage, but i really like my 2008 Mega Cab Dodge 4x4.

srbeck65 - Posted May 5 2008 06:26 AM

7. I would also like to get rid of my dpf and cat. I found a dpf kit at www.dieseltruckchips.com, I haven't got one yet but planning on it so. I haven't had any problems with MPG get 14 city 21 hwy. I just want to see the smoke. Ik anyone as gotten one of these kits I'd to know how it works
2007.5 6.7L cummins 4x4

tick33 - Posted June 8 2008 03:11 PM

8. I own a 2008 Chevy Silverado 2500HD w/a Duramax LMM

This is the second time this situation has happened. The first time was about 3 weeks ago and it seemed to correct itself after about 20 miles of driving so I thought it was a fluke. This time, it's lasting longer. Here's what happens: I'll be driving along on a level road and suddenly, the average economy indicator drops to under 9 mpg (down from 16-18) and stays in that range for 20-40 miles. The engine doesn't sound or seem to run any differently but I have noticed a diesel odor which I hadn't observed at any time before the two episodes. Also, the fuel gauge indicates a much more rapid use of fuel - like 1/8 of a tank for my 25-mile round trip to work.

Steve229 - Posted June 27 2008 08:20 AM

9. I have an 08 F250 crew, short bed. I put on a Juice with attitude tuner to see if I could help the mileage. No help! Nothing will help as long as the DPF is on the truck. It restricts the exhaust by about 90%. Changing mufflers, air filters or chips won't help. You have to get rid of the DPF first.My dealer said it's against the law and he'll void the warranty. He put's up with the tuner but doesn't like it.
Regen averages once per tank. Mileage drops significantly during regen. It's just plain stupid engineering. Who's hurting the world the most, the guy getting 14 mpg or the one getting 20??? It's like the smog pump, maybe they'll get there acts together and figure out a better way. Meanwhile if you can avoid buying a new truck then don't buy one yet.

bstew - Posted August 28 2008 06:48 PM

10. I have a friend with a 2008 F250 6.4L. His fuel economy is in the 12 range most of the time. When he is towing, he is in the 8-9 range.

I had a 2006 F150 gas that got 12 empty and 8 towing a comparable trailer for the size of the truck.

He is currently selling his F250 as he has had entirely too many problems with it. The first was a computer failure. The second was an electrical failure, and most importantly, the third was a fire in the exhaust caused by the filter. His truck let out a large cloud of white smoke that made him thing he had an engine failure. The truck went into a safe mode, and instructed him to stop quickly. He did so, the engine stalled and would not restart.

After having the truck (not the trailer) towed to a dealer, they were able to get him back up and running, but they left his RV sitting in a very bad part of town, and would do nothing to help him.

Following that, I decided I would not buy a new Ford. Mostly because of the horrible fuel economy, but secondly because they left him in a dangerous part of a strange town with no way of moving his RV. I have since purchased a 2005 dodge 2500, and although I've had it only a few days, am averaging 20-24mpg with no load, and am very pleased.

locutus2k - Posted October 25 2008 06:18 PM

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