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Words of wisdom from the DPF Doctor

By autotech-nath on January 22, 2022

If you were fortunate enough to attend The Big Weekend recently you will have met Darren Darling, founder of the, now global, DPF Doctor Network. In the last 10 years, Darren has established himself as a genuine DPF expert, so much so that he bottled his ‘secret sauce’ by founding the network and has since been joined by over 120 DPF Doctors. It’s a number set to double in 2022. There are now DPF Doctors in Australia, Holland, Ireland, and the UK with many countries in between; with every top technician proudly bearing the logo of the DPF Doctor Network, committed to upholding the standards set by Darren and equally committed to ongoing learning via Darren’s live and interactive online training, the DPF Doctor portal and the DPF Doctor members’ forum. At The Big Weekend, Darren spoke about a common trend he and his doctors have been seeing over several years – namely, the misuse of products and damaged beyond repair DPFs. Such is his passion for this subject we were delighted when he took some time out of his schedule to write a few words for us.

Damaged DPF’s and the misuse of additives…

“Something we are seeing at an alarming rate is damaged DPF’s that are beyond repair,” says Darren. “The unfortunate thing for the motorist is that in most cases it has been a mechanic that has caused the damage. The most common causes of damage are forced regenerations when it is not safe to do so, resetting DPF adaptations when it is not safe to do so and the misuse of DPF additives.

“In my opinion, if you do not know what effect a reset or adaptation has then don’t do it. If you are not sure if a regeneration is safe to carry out, then don’t do it. And if you are not sure what effect an additive has then don’t use it! However, all of these things can be overcome with some training or some self-learning on fault-free vehicles. If you spend some time out on the road recording live data to get familiar with that type of car, this will give you a benchmark with some good DPF data. If you are using in-tank DPF additives, then repeat this process with and without the additives and this will show you if the brand of additive is safe to use with a blocked DPF.

My advice is that if you see an increase in exhaust temps of 100 degrees centigrade then this is not safe to use in a blocked DPF. However, it can safely be used as a preventative measure. Although we are looking for around 550 degrees during regen, we do not want to be seeing 700+ degrees as the ECU can lose control of the temperature if the soot is excessive and the additives are increasing the temperature. Additives like the JLM Lubricants’ DPF Cleaner that don’t increase the temperature are a safe option to use. We see vehicles where the DPF has been damaged beyond repair because the additives used have a high iron content. This, combined with a forced regen, has led to the DPF melting from within. Mechanics must ask their customer what products they have used before bringing their vehicle in, and if another mechanic has undertaken a forced regen. Too many of both and the DPF is heading to the scrap heap with the motorist left with a huge bill through no fault of their own.”

Darren’s views are also mirrored by Mike Schlup, the MD of Kalimex, the UK distributors of the JLM Lubricants product range. Mike also attended The Big Weekend. This is what he has to say:

“Look at fuel additives as you might look at medicines. Bit of a headache? You might reach for a couple of paracetamols, following the recommended dose. You would not just launch into the packet contents with disregard for the consequences because that could cause you harm. Headache persists?

You would probably seek advice from your GP to find the underlying cause of the problem. In the same way, if you get a warning light or code on the car for a problem such as the DPF, then you can try a decent quality additive to see if that helps. If the problem is solved, happy days. But if it persists after using an additive there is no point simply using more of the same additive as this can lead to a myriad of problems. As Darren says regularly, adding multiple bottles of DPF cleaner, especially the cheaper iron-based formulas, will cause the filter core to overheat and melt resulting in permanent damage, especially if this is combined with forced regens.”

“DPF and diesel emissions faults are a complex area, especially on the more modern diesel engines. The adage of a quick thrash down the motorway is simply out of date and is flawed advice. Always seek specialist advice from a DPF Doctor for example to find out exactly what is wrong. A DPF warning could be caused by a whole host of underlying issues so if in doubt, put the brakes on and before you write the prescription, make sure it is the right one. Your customers will thank you for it.”

If you would like to find out more about becoming a DPF Doctor and the many benefits of being a top tier mechanic, part of Darren’s DPF Doctor Network, please visit To find out more about JLM Lubricants trade-trusted products, including their iconic DPF cleaning product range, visit



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