Diesel Tech Q&A: Diesel Deletes

Diesel technician working on Duramax engine
“Deletes” are probably more common on diesel pickups than winches. Removing the pollution-control hardware eliminates many of the maintenance and performance issues related to exhaust gases recirculating back through the intake system. But the question for the owner is, “Do the pros of such modifications outweigh the cons?” Photos by Bruce W. Smith

Diesel Deletes, Good or Bad?

I have a 2013 Chevy 2500HD. I’ve heard of people removing the diesel exhaust fluid (DEF) system to get better performance. This seems like a complicated process. I’m assuming this would involve a new CPU chip. What if I needed to take the truck to the dealer for service? Would they still service it? The truck has 65,000 miles on it, but I would wait until the warranty ended before I did this.
Warren Maziol, Lockport, New York

I have a 2012 GMC 3500 Duramax. I am being told to have it “deleted” by most everyone. What is your opinion? Advantages and disadvantages?
Richard J. Downing, Ahsahka, Idaho

Great questions, and ones just about every RVer has asked at one time or another if their diesel pickup is equipped with a pollution-control system that requires the use of diesel exhaust fluid (DEF).

Duramax EGR cooler
A typical Duramax EGR cooler that has become plugged as a direct result of the pollution-control system doing its job. This one was removed and replaced with a new one. The engine in this trailer-toting Crew Cab had less than 60,000 miles on it.

Removing the DEF components is just one step in what those in the performance-diesel circles call doing a “delete.” Emissions-related components on diesels are there to reduce the amount of harmful nitrogen oxides (NOx) and exhaust particulates released into the air. Diesel exhaust is dirty, and at some point the oily soot and carbon buildup from the exhaust recirculating through the engine will clog up the EGR valve, EGR sensors, EGR cooler and diesel particulate filter (DPF), and gum up turbo vanes. Performance and fuel economy fall off as these components plug up, and the frequency of your Duramax’s “regens” will increase in frequency trying to keep the DPF clean.

When that time comes, the emissions-related parts have to be cleaned or replaced. Some diesel owners opt for deleting all the “offending” pollution-control components instead of cleaning or replacing them. The entire EGR delete process takes a savvy diesel tech about a day to complete, including taking out the DEF system, removing the catalytic converter and DPF, and installing a new exhaust.

engine-control computer
When an EGR “delete” is done, a software “tune” has to be uploaded into the engine-control computer so trouble codes related to missing components aren’t tripped. Such performance software also makes changes to fuel, timing and other engine and drivetrain parameters for improved power.

Doing a delete of this type also requires reprogramming the engine-control unit (ECU) with a “tune” or “tuner” that replaces the OEM software with new programming that controls fuel delivery and engine timing. The tune/tuner also works around the onboard diagnostic system (OBD), which continuously monitors the engine operation parameters, making it think all is well so no emissions-related codes are thrown because of the missing components.

When all is done, the soot-clogging issues caused by exhaust gases recirculating back through the engine are alleviated. Depending on the tune/tuner, the result is slightly quicker turbo spool-up and throttle response, and an increase in horsepower/torque. How much power is gained is totally dependent on the tune and the engine hardware. Fuel economy may improve by 2 to 3 mpg, but, again, that depends on the aftermarket-software programming. Remember, it takes fuel to make power in a diesel. A heavy foot to achieve more power means using more fuel, thus less mpg.

Legality of Deletes

Now to the elephant in the room — the legality of deletes. It’s simple: They aren’t. Removing or tampering with anything related to pollution-control components is a direct violation of the federal Clean Air Act (CAA). If you, or the shop doing the work, is caught and prosecuted, the EPA can assess a fine of up to $4,527 for each “tampering event or defeat device,” in accordance with Section 205(a) of the CAA, 42 U.S.C. § 7524(a), and 40 CFR Part 19.

Tampering with or removing pollution-control components also voids the engine warranty, according to GM, Ford, Ram and Nissan warranty policies. Then there’s the resale and trade-in aspects to consider. The resale of a diesel pickup that has had the engine modified isn’t specifically addressed under the federal law. However, state or local laws may require vehicles to be “smog legal” for them to be licensed or registered.

Restoring a diesel pickup’s pollution-control components back to OEM can cost $4,000 if all the parts have to be replaced and reinstalled. The DPF, alone, can cost upward of $2,000 for your truck. Will a dealer service a truck that’s been modified in this way? Sure. Servicing a diesel that’s been “deleted” is the same as servicing any other diesel — you just don’t have to deal with EGR-related problems.

The diesel particulate filter (DPF) is removed.
The catalytic converter and diesel particulate filter (DPF) are removed when an EGR delete is done, eliminating the necessity for diesel exhaust fluid (DEF). Replacing a DPF on a Duramax can cost more than $2,000, so it pays to keep the original parts in case the pollution-control system has to be reinstalled.
Removal of defective pollution-control device.
It’s fine to remove and replace defective pollution-control devices, but completely removing or altering anything related to pollution-control components is a direct violation of the federal Clean Air Act (CAA).

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Bruce W. SmithA respected automotive and RV journalist and longtime Trailer Life contributor, Bruce W. Smith has held numerous editorial titles at automotive and boating magazines, and authored more than 1,000 articles, from tech to trailering. He considers his home state of Oregon a paradise for RVing and outdoor adventure.

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  1. Like anything else, what is the cost-to-benefit ratio? As a state trooper working the interstate highway, I would see what we referred to as a disabled vehicle as having a “high tinker factor.” If the vehicle is tinkered with enough, eventually it will fail. Leave things alone as designed. If not, you own it and the consequences. If a trooper sees a diesel, or any other vehicle, smoking, the vehicle is stopped and inspected. If the anti-pollution is deleted or modified, the vehicle is grounded and taken out of service. Then things really start to happen, with not so pleasant outcomes.

  2. I owned a 2010 GMC 2500 truck that had been “deleted” by the previous owner. It sounded great idling because the muffler had also been deleted, but it was noticeably noisy while driving with our fifth-wheel attached. It had crazy power, which is why I bought it. It also was very smelly, and I received many complaints from neighbor RVers when I left it idling in our RV park while it warmed up. In 2016 it began going in to “limp mode” while driving, with the incidents increasing in frequency daily while we wintered here in Tucson. I could pull the truck over and turn off the engine, which reset it, but that felt dangerous while pulling your fifth-wheel. When I took it to the GMC dealer to have it “repaired,” they were unable to determine the cause because the truck no longer showed any fault codes. As full-timers, we no longer felt confidence in that truck, so we sold it and purchased a 2017 Chevy 2500. I suggest leaving the truck OEM. The cons outweigh the pros in a delete scenario.

  3. What about diesels that are older and don’t have the DEF system? Mine runs fine, but I want to put performance parts on it, like a better turbo, tuner, etc. Is that legal?

  4. I agree with Jim. Tampering with the emission system on modern diesel engines is not a good decision. The systems are there for a reason, they clean the air our children breathe. I am a master auto technician and work on a lot of newer diesels. Many customers have asked me about the “delete,” and I try to educate them. Lots of problems usually arise down the road, some of them major. The tune devices usually increase the boost pressure and can lead to head gasket failures. I pull a big toy hauler with my Ram dually 6.7L and I have never felt the need for more power. I suggest you find a truck that can pull what you need easily and maintain it well. Just plan and budget on having a major emission maintenance around 150k.

    • Nevada Highway Patrol has a unit dedicated to “smog.” They use a piece of equipment that measures the exhaust as you drive by. Normally, this is directed at semis, but if they see a passenger truck “rolling coal” (black emission), they can tell instantly if you are within guidelines. Think radar and how quick it can measure your speed. Same idea. I now live in Wyoming, and the legislature passed a “rolling coal” bill. Just do the right thing and you won’t have issues with state police or troopers.

      • I say you are full of it. I drive professionally, and they have been talking about exhaust-reading equipment that can test our big tractors for more than five years, and still nothing like what you describe has ever come into existence. They do have equipment where they place a boot over one of your stacks and get a readout, but it only tells them the pollution levels you’re emitting and is not a direct indicator on whether the trucker has either deleted or tampered with their DPF system. The people that blow out the black smoke is not a result of a deleted DPF system but rather the fact that the program they selected is extremely pushing the motor for more speed and torque. I set my tractors for a moderate program that gives me about a 25 percent increase in power and increased fuel efficacy of 1.5 MPG. 1.5 MPG improvement is massive when you turn between 100,000 and 150,000 miles per year. I also keep the stock mufflers in place so the tractor is still quiet.

  5. I have a stock 2012 Chevy Duramax with 136,000 miles. It’s been totally trouble free, except for the emissions system. Two years ago, on a “bucket list” trip to Alaska, I had a DEF tank heater failure that put me in limp mode 120 miles from Whitehorse. With a 150-mile allowance mandated by those bright bulbs at the EPA, I returned to Whitehorse to wait a week for a new tank to be installed by the Chevy dealer. Mind you, there are three heaters in the tank, any one of which can do the job in cold weather, and it was summer, so this was an unnecessary, artificially created problem. Adding it all up, the eventual replacement of my DPF, EGR components and SCR system will cost over $10,000, and that doesn’t include the time bomb that is the CP4 pump. I love my Duramax, but I hate what the EPA has forced GM to do to meet emissions requirements. It’ll be my last Duramax, unless I can find an older, rust-free southwest truck. More likely, I’ll go back to a half- or three-quarter-ton gasser and a smaller RV.

  6. Jim Volner hits it on the head. Anyone believing that a dealer will cover your butt if something goes wrong when your truck is under warranty will also be in trouble. It’s nice to have the power, but the mileage isn’t worth it.

  7. As a Ram dealer, let me advise everyone that no good will come from deleting your emission devices from your vehicle. It is against federal law and will make your vehicle worth less money. I am the first to agree that they are too expensive and cause problems, but not near as many as deleting will. Most service problems we see are from deleted vehicles. My best advice is to never own a late-model diesel out of warranty!

  8. I like the idea of having cleaner air for my grandkids. I have a new 6.7L Power Stroke that I feel has plenty of power, and any more is just an eco trip, as far as I’m concerned.

  9. Coworker of mine was traveling through Alaska when his six-month-old Ram 2500 went into limp mode 3.5 hours south of Fairbanks, 4.5 hours north of Anchorage. Sure, the truck was under warranty since the DEF tank sensor failed showing his full tank as empty. The dealership towed his truck home to Fairbanks. The trailer towing came out of his pocket.

  10. I have a Winnebago View on a Sprinter chassis. I got a tune from Green Diesel, and my fuel mileage increased and so did my power. About 6,000 miles later, in Alberta, Canada, I burned a hole in piston number 5. The repair cost me $6,000. About 8,000 miles later, I burned a hole in piston number. I had a manufactured engine installed at a cost of $9,000. I now have the factory standard setting on the computer and hope to have no more such problems.

  11. I can only say this. What else can one expect this magazine to say? It has to tow the line and agree with the emission laws. That said, I agree with their line of reasoning though. My issue? I have an ’05 Ford Excursion and that engine had a few bad systems…the EGR system being one. The only answer was to delete it, as neither Ford nor Navistar ever came up with a decent fix. The aftermarket did, but the system was deleted when I bought the vehicle. It has no DEF system…thank goodness. I am extremely pleased with my “bullet proofed” Excursion.

  12. I’m reading a lot of socialist answers here. First to Sheldon and Jim, do you ticket people with vehicles older than 2008 or ’09, because most if not all did not have all this emission crap on them, so yes they smoke, which is what diesel engines do. My law-enforcement friends that own diesel vehicles also do deletes and have zero issues. In order for these vehicles to run correctly, they have to be able to breathe in and exhaust out. Most deleted engines see a 20% increase in fuel economy, reducing emissions and fossil-fuel use. Every diesel mechanic I know, including the ones at the Ram, Chevy, and Mercedes dealerships, agree that these emissions systems only create more issues and are not keeping our environment any cleaner. It only makes more money for dealers and the government at the expense of the owners. I have been left stranded multiple times by these systems that never work as intended, and I am expected to spend 50K plus for a vehicle and then spend 10K about every three to four years to fix a system that is totally unreliable? All these mechanics on this discussion want your business so the will say the things that make them money. These are the same mechanics that can’t truly fix vehicles, as they are just parts replacers, and you have to foot the bill for their incompetence. The thought of our government arresting and fining you for modifying and repairing your own vehicle is just another case of the socialism embedding in our nation.

  13. Regarding Ford’s 6.0L diesel EGR system, 2005: I was told that the F-450 and up did not have that EGR system, so it seemed OK to eliminate it without any problems with the operation of the engine. The internal oil cooler was showing its trouble code, so it was changed at the same time. My mechanic had me buy an aftermarket tuner to be able to shut off the EGR light on the dash. However, the next time I went in for something at my Ford dealer, he was not able to use the computer to access the truck’s computer. I should have reset my computer back to stock before I went in for service. My aftermarket tuner only works one time, so somehow the service manager was able to get in anyway, and he was able to fix the issue that day, and I think he went deeper into the levels of the menu and turned off the EGR light light. He did not tell me what he did as probably it was illegal for him to do so. I did not ask him either. The result of all of this is the truck runs great, although it always did before. Fuel mileage increased somewhat, 1 or 2 mpg, but at least I have the peace of mind that the EGR won’t cause any issues later down the road. Mileage is now at 170,000.

  14. Is there anything you can add to the fuel that would help keep the emissions system clean ? Thinking preventive maintenance here.

  15. I have a 2009 Duramax 2500HD. I had it deleted when my DPF filter was completely clogged and shut it down. I checked into replacing the original parts, and it was a ridiculous price. My truck does not smoke at all, and I get 12 to 14 mpg towing my Surveyor travel trailer. When I’m not towing, I get 22 ti 24 mpg on the highway. My motor breathes like it’s supposed too. We have too many regulations based on this climate-change crap being pushed on us nonstop by the leftists and their counterparts the liberal media. Way too much government going on anymore. Oh well, I got sidetracked. I’ll take my chances! I agree with Jim Coleman!

  16. It’s my belief that diesel emissions systems are at the point where gasoline emissions systems were in about 1980. At that time, catalytic converters were in use (starting 1975 except for the Honda Civic, which was clean enough without it), but engine power was low — lots of work with lean-burn systems, timing adjustments, etc. If you were around in the 1960s in any major city, you would understand that those pollution controls were absolutely necessary to protect public health. This was a time when you could almost slice the air, and scientists worried that the particulate pollution would block sunlight eventually and cool the planet.

    Diesel engines are very efficient, but we haven’t achieved the combustion completeness present in today’s gasoline engines just yet. As a result, extra maintenance is required for the near future, and it’s not free.

    As to pollution controls being rampant socialism, I offer two points. First, pollution is simply a concentration of waste products greater than that which nature can break down. In the country, with light traffic, natural systems can break down the amount of diesel particulate produced. In a large city, this is not the case at all. It’s not cost-effective for manufacturers to produce a “rural” model which can be operated only in rural areas.

    The second point is that police, fire, national defense and highway systems are all socialistic by nature, and that is not a bad thing. The Fire Department emblems of old were sold to subscribers and placed on your house. If your house caught fire, the firefighters arrived and looked for the emblem. If no emblem was found, your house was allowed to burn to the ground. While this system still exists in some parts of the South, most jurisdictions have decided that it’s more effective to fund fire departments with property taxes, and cover all buildings.

    • Mac Walker, I don’t know where you are from, but I am close to 60 years old and lived all my life here in the South. I have lived in the deep, deep South and all over, and I have NEVER seen, in this modern age, what you describe about fire departments not coming to your aid if you didn’t have an emblem on your house! I would think that is a disrespect of firefighters everywhere in this nation. I don’t think you know what you are talking about except a bunch of socialist mumbo jumbo! As you said, back in the ’70s and ’80s gas emissions where viewed as creating another ice age, and now they are saying it’s going cook the earth. These so-called environmental scientists don’t know squat! I know for a fact that this earth has heated up and cooled down thousands of times, and we are just in the midst of another cycle. Yes, we shouldn’t needlessly pollute our earth (streams, land and air), but to do the things like these socialists want us to do is beyond pale. As I said, we as consumers should not be forced to be test subjects on these emission systems that are failures. I should not be forced to purchase a $50K-plus vehicle and have to replace a system every couple of years at a cost of $10K or more. I just spoke to another gentlemen the other day that has the same vehicle as I do and had all the same issues I did and ended up spending close to $20K until a guy at the dealership finally told him that the only answer was deleting all that crap. He said he has had zero issues since and gets 50% or more better fuel mileage.

  17. Interesting comments from folks that have deleted the DEF/EGR systems from their 2009 and 2010 Duramaxes. 2011 was the first year GM put that stuff on their trucks. Just saying…

  18. I have a 2011 6.7-liter Power Stroke, and the filter finally clogged up at 315,000 km. My choice was $7K CAD to replace or $1.8K CAD to delete. Not a hard chioce. Yes the filter and DEF addressed the Nox, but I’m not convinced the net pollution improvement was any better when considering the extra fuel consumed, with exception to the Nox. Very pleased with the extra HP and fuel economy.

  19. Thank you for covering the legality of the deletes. My friend owns and operates a large truck and needs heavy repairs. He’ll have to get the right help fixing it and avoid a delete in case it’s illegal.

  20. I found it interesting that you said that tampering or removing pollution-control components voids your warranty. I have a friend that has a diesel car and it is hard for him to find a good mechanic. I’m going to help him look online for a good place to take his car for repair.

  21. I am sitting here seething at the pending cost of either deleting my DEF system ($2,400), fixing it ($6,000+) or having to trade my 2016 F-250. Of course, my dealer (the one that sold me the truck) wants to sell me a new one, and then when the factory warranty wears off, sell me a new one when the DEF again fails. Shame on Ford for their poor quality and making money off of me. This truck had an expensive repair ($3,500) with the “torpedo” part of the exhaust system when it was only a year old. Wondering if I have a lemon.

  22. I’m updating my previous post, having now accumulated 158,000 miles. I’ve started an oil analysis program with Blackstone Labs, and both my Duramax and Allison are reported to be exceptionally clean. I’ve had no further problems with my DEF/SCR/EGR systems since the DEF tank problem 3 years ago. I’m going to stay completely stock, keep using a lubricity enhancer for the CP4, and focus on preventive maintenance. I’ll update here if anything significant happens. May the Force be with me!

  23. Since it is against the law to remove the DEF system, then it stands to reason that it is also illegal for a dealer to knowingly sell a truck that has been deleted, right? I have never owned a diesel before and knew nothing about the legalities with the EPA. My salesman told me the DEF had been deleted, and my wife asked if that was legal, and he just said people do it all the time to get better mileage. It wasn’t until I got home with the truck and after researching found out there could be a $4,000+ fine, not to mention a voided warranty and not being able to pass a smog test. So what are my options? I bought the truck Saturday, and the dealer is closed on Sunday. Help, please!

    • Yes, removing the SCR, DPF, DOC, is illegal and dealers are asking for trouble if they sell a vehicle so modified.

      DEF is an aqueous urea solution injected into the SCR. People fixate on DEF because it has a separate tank and requires occasional attention. The real P.I.T.A. is the DPF, Diesel Particulate Filter. This is one big cigarette butt to trap soot. The problem is it has to be burned clean every 250 miles or so by dumping raw diesel down the exhaust. On 2008 Powerstroke instantaneous MPG dropped from 15 to 7 for 10 minutes at 70 MPH. That is an extra 0.9 gallons of diesel. Other problem is the raw diesel came from firing direct injection while exhaust valve was open. Some of this washed cylinder walls and diluted engine oil. Was common for oil level to rise 1 quart every 5,000 miles due to diesel in the oil.

      Mercedes-Benz seems to have done a better job on 2009 ML320 Bluetec by insulating the DPF letting it run hot all the time to burn itself clean. I never detected a regeneration cycle. Never saw huge drops in MPG during 500 mile days on interstate.

      Now very happy with a simple gasoline F-150.


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