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DPF FAQs from Automotive Enthusiasts

Welcome to a comprehensive collection of frequently asked questions (FAQs) about Diesel Particulate Filters (DPF), sourced directly from automotive forums and enthusiasts. Whether you're curious about DPF maintenance, potential issues, or modifications, this compilation offers insights from experienced car owners and technicians. Let's dive into the world of DPF systems and explore the valuable expertise shared by enthusiasts like you.

DPF FAQs from Automotive Enthusiasts-chevrolet

Q: Can a DPF be cleaned or does it need replacing?

A:If totally blocked, it will need to be replaced. Normally, you periodically (every 4 weeks minimum, depending on how many kilometers you drive per week) drive the vehicle at around 80 km/h or above for at least 10 minutes to burn off the particulates.

If the DPF light comes on, drive the vehicle out on the highway for some 15 to 20 minutes, and the light should go out. If you take it to a dealer, they should run it on a cycle to clear it, which is basically getting the DPF up to a temperature where the particulates can be burnt off.

Some diesel engines have a system of injecting some diesel into the exhaust or by injecting some on the exhaust stroke so that it does not increase the developed power but adds exhaust heat, seeing as diesels are normally running with an excess of air, and this aids in heating the DPF to temperature to clear it. This is managed by the ECU.

Q: What happens if I use DPF oil in a non-DPF car?

A: Nothing much happens if you use it in a non-DPF vehicle. There is no benefit to be realized by doing this, and you will be paying for specialized oil characteristics that are unnecessary for your vehicle.

Q: Is a DPF the same as a catalytic converter?

A:No. DPF stands for Diesel Particulate Filter. It traps soot. There IS a catalytic converter in diesels; the box after the DPF is the SCR, Selective Catalytic Reduction. It combines the exhaust with the DEF in the presence of the catalyst to convert the NOx into nitrogen and water.

Q: If the EGR is blocked off in a diesel engine, can this affect the DPF in any way?

A:Yes. Diesel engines run inefficiently at very low revs because they often do not have complete combustion. Without the EGR valve operating, poorly burned mixture passes through the DPF at low revs, leading to sooty exhaust that can clog the filter. It may be worth either doing a forced regen of the DPF or ensuring your car’s conditions for a normal regen are met to allow the car to do its own on a reasonably regular basis. Conditions for a regen are more than half a tank of fuel, oil temp above around 65 deg C, and an uninterrupted 30–40 minute run after the oil is hot with not dropping below 40 mph.

Q: Can a blocked DPF cause low oil pressure?

A:No, a blocked DPF won't directly cause low oil pressure. However, it can lead to extreme exhaust back pressure. If the HC doser is stuck open, fuel may enter the exhaust, potentially affecting fuel rail pressure.

Q: What kind of oil does a catalyst DPF (diesel particulate filter) require?

A:The catalyst DPF system uses diesel fuel for engine operation. However, it also utilizes a urea-based liquid called "Adblue" for emissions control. The Adblue tank is separate, and its usage is regulated by the engine control unit (ECU). A full tank of Adblue can last through several vehicle services. If your vehicle has a catalyst for controlling NOx emissions, it may have a low-level warning light indicating when Adblue needs to be topped up. Dealerships usually handle this during service, but owners can top up the Adblue themselves following the instructions in the owner's manual.

Q: How long does it take for a diesel particulate filter (DPF) to block short distance city driving?

A:If you consistently drive short distances in the city with habits like stopping just after engine warm-up, frequent intensive accelerations with a cold engine, and immediately stopping the car whenever the engine control unit (ECU) initiates a forced DPF regeneration, it may take as little as one week for the DPF to become blocked. In extreme cases, the car may become immobilized within one or two weeks, and there's a possibility that the filter could be damaged beyond repair.

Q: Can you drive with a blocked DPF?

A:In some cases, when the diesel particulate filter (DPF) becomes clogged, the engine may enter "Derate Mode," severely restricting horsepower to prevent damage. While you may still be able to drive the vehicle for a short distance at reduced speeds, it's essential to seek immediate roadside assistance from a qualified technician. Continuing to operate the vehicle beyond a certain point may result in the engine shutting down completely, necessitating a tow truck.

Q: How do I get rid of a DPF warning light?

A:When the DPF warning light illuminates, it indicates that 'passive regeneration' has failed, and active regeneration of the diesel particulate filter is required. To initiate active regeneration, you can increase your speed to over 40mph for 10 to 15 minutes. Some recommend driving at speeds exceeding 60mph for at least 15 minutes to effectively clear the filter. After the regeneration process, you may need to switch off the ignition and wait a few minutes for the ECU to register. This method can be more cost-effective than visiting a garage with specialized diagnostic equipment.

Q: Is muffler delete illegal?

A:Yes, in many places, muffler delete is illegal due to increased noise levels beyond legal limits.

Q: Do all diesels have DPF issues?

A:DPF problems are more common in vehicles with smaller filter systems, like light-duty trucks and cars, due to quicker clogging. Larger vehicles, especially heavy-duty trucks, tend to have more robust DPF systems and encounter fewer issues. Short-distance driving, particularly under heavy load, accelerates DPF clogging, while freeway driving typically results in fewer problems due to automatic regeneration. Overall, unless opting for heavier-duty vehicles, most diesel trucks face emissions-related challenges.

Q: Does removing DPF cause black smoke?

A: Yes, it can. The DPF (diesel particulate filter) acts like a massive cigarette filter for the engine, capturing soot and carbon from the exhaust. Without the DPF, the exhaust would emit darker smoke. However, black smoke can also result from overfueling issues.

Q: Can red dye harm a diesel DPF system?

A:No, red dye in diesel fuel typically indicates non-taxable use. In the past, using red dyed diesel in trucks with Emissions Aftertreatment Systems (EAS) could cause DPF blockages. However, with the adoption of Ultra Low Sulphur Diesel (ULSD) for both taxable and non-taxable diesel, this issue is less common. While it's illegal for taxable use, red dye itself doesn't harm the EAS system, especially since off-highway equipment now uses ULSD compatible with EAS.

Q: Can a blocked DPF cause an oil leak?

A: Yes, it will overpressure and overheat the engine, potentially leading to gasket damage.

Q: DPF delete horror stories?

A: "I've been running it deleted and tuned for about 80k miles with no issues."

Q: How can I delete the DPF system in my vehicle?

A: Illegally.

Q: What does that do to one's ability to resell the car?

A:"I have all required parts to return to stock configuration should I ever sell and the person buying request a stock vehicle."

Q: Has a single person ever been pinched for this?

A:"There have been numerous successful lawsuits against companies that do modifications like this, usually they are large scale offenders."

Q:So nobody ever has any troubles with it? Just so long as they can register wherever doesn't care?

A: "I lived in SoCal for years with my car deleted. I kept out of state plates."

Q:What if you were driving through somewhere that required it and you broke down? Would you sweat at all?

A:"Yeah, I prepared some basic tools, They live in a box in the attic of the garage just in case."

Q:Also what would you need to do to return the software to original?

A: "If you buy the flash tuner you can flash it back to stock anytime you want."

Q:How do I clean the DPF?

A: "I took it to the shop and was told to run a cleaner in my tank."

Q:Do you think DPF deletion is effective?

A: "I really have no idea, but if it works and saves you a 2000 dollar part it may be worth it. Next time my DPF clogs I'll be looking into it."

"I have deleted my cat dozer years ago, best decision in my life."

DPF FAQs from Automotive Enthusiasts-Ford


From these discussions, it's clear that automotive enthusiasts have a wealth of knowledge and experience regarding DPF systems. Their insights provide valuable understanding for other car owners to better manage their vehicle's DPF systems. If you have similar questions or experiences to share, feel free to join the conversation and delve into topics of automotive technology and maintenance with us! SPELAB will continue to stay tuned for more technical issues regarding DPF, and we'll keep updating to provide you with more valuable information.

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