How to Clean a DPF Filter (Regeneration Guide for Diesel Trucks)

If you own a diesel truck built after 2007, you have a DPF. Diesel Particulate Filter. It catches soot before it leaves your exhaust. And every so often, it fills up and needs to burn that soot off. That process is called regeneration, and if you ignore it long enough, your truck will punish you for it.

I have cleaned and replaced more DPFs than I can count. Here is what I tell every customer who walks into the shop with this problem.

What a regen actually does

Your truck injects extra fuel on the exhaust stroke. That raises exhaust temperatures to around 600°C, which burns the trapped soot into ash. Takes 20 to 40 minutes. The truck does it by itself most of the time and you never notice.

Problems start when regens keep getting interrupted. Short trips to the grocery store, idling in the driveway, shutting the truck off mid-regen. Do that enough times and the filter clogs past the point where the truck can fix it alone.

The three types of regen

Passive regen happens during normal highway driving. Hot exhaust, steady load, the soot burns off on its own. If you tow or do highway miles regularly, you may never think about your DPF.

Active regen is when the truck notices the filter getting full and starts one itself. You might see a message on the dash, notice slightly higher idle, or smell something hot. Let it finish. Keep driving until the message clears.

Forced regen is the one you trigger with a scan tool, or the dealer does it for you. This is for when the filter is badly clogged and normal driving cannot clear it. Costs a couple hundred bucks at a shop.

What to do when the DPF light comes on

1. Do not shut the truck off. Keep driving.
2. Get on the highway and hold 100 km/h or more for at least 30 minutes. Steady speed matters more than speed itself.
3. Do not tow heavy during a regen if you can avoid it, but normal highway cruising is exactly what the truck wants.
4. If the light does not clear after a good highway run, book a forced regen. Do not keep driving on a clogged filter.

Can you clean a DPF yourself?

You can buy DPF cleaning additives and pour them in the fuel tank. In my experience they help a little with light buildup and do nothing for a badly clogged filter. They are maintenance, not repair.

The proper cleaning methods are:

• Thermal cleaning — the filter is baked in a special oven, then air blasted. Most professional DPF cleaning shops do this. Runs $300 to $500 in Canada.
• Aqueous cleaning — water based flush systems. Also effective.
• Replacement — when the filter is cracked or the substrate is damaged, no cleaning saves it. OEM filters run $2,000 to $4,000 depending on the truck.

How to make your DPF last

• Drive it like a truck. Regular highway runs are the single best thing for DPF health.
• Do not idle for 30 minutes every morning in winter. Five minutes is plenty, then drive gently until warm.
• Use the correct low ash engine oil for your truck. Wrong oil clogs DPFs faster. Check your manual.
• Fix check engine lights promptly. A faulty sensor can stop regens from happening at all.
• Do not ignore the warning light. Ever.

A DPF that gets regular highway time and proper oil will often last the life of the truck. The ones I replace are almost always from trucks that spent their lives doing short city trips. The filter is doing its job. Give it the conditions to do it.

Frequently asked questions

How long does a DPF regen take?

20 to 40 minutes of steady driving. If your truck starts one, keep driving until the dash message clears. Shutting off mid regen is what causes problems.

Can I drive with the DPF light on?

Drive straight to the highway and do a regen run. Do not keep driving normally for days with the light on. The filter keeps clogging and you risk a very expensive replacement.

Should I use DPF cleaning additives?

They help a little as maintenance on a healthy filter. They will not fix a filter that is already badly clogged. For that you need professional thermal cleaning or a replacement.