What Is an OPF? Petrol Particulate Filters Explained
FixMyCar explains how petrol particulate filters work and which cars have them.
Book a car repair nowEllie Dyer-Brown
Tuesday February 25 2025
5 min read
If you’ve bought a petrol car recently, the chances are it has a petrol particulate filter (PPF), sometimes called an otto particulate filter (OPF). But what does this mean for you as a driver?
The good news is that unlike a diesel particulate filter, which can be a bit of a headache to maintain, PPFs pretty much take care of themselves. This guide takes a closer look at how they work, which cars have them, and whether they can be removed.
What is a petrol particulate filter?
A petrol particulate filter is a clever bit of tech designed to reduce emissions and keep the air cleaner.
PPFs are highly effective at getting rid of exhaust particulates, resulting in a decrease of about 90-95%.
Why were petrol particulate filters introduced?
Regulations around car emissions have been getting stricter over the years. Back in 2009, the EU5 standard set the first limits for petrol car emissions and required all diesel cars to have a particulate filter.
Then, in 2018, the EU6c standard tightened things up more, setting a NOx limit of 60mg/km for new petrol vehicles and 80mg/km for diesel vehicles.
Complying with these requirements presented a new challenge for manufacturers, who rose to the occasion by introducing petrol particulate filters in many cars. PPFs have enabled particulates and nanoparticles to be virtually eliminated from exhaust emissions.
How do petrol particulate filters work?
The particulate filter is located downstream of the catalytic converter inside a metal box that looks a bit like an exhaust silencer. It contains a ceramic honeycomb structure, just like a DPF, and is located close to the turbocharger so that it heats up quickly. High temperatures are key for eliminating nasty particulates.
When exhaust gases flow through the PPF after exiting the engine, unwanted nitrous oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) particulates are burned off, producing a little carbon dioxide, water and nitrogen in the process.
After this, gases pass through the catalytic converter (pictured above), where a similar process occurs. The result is that any exhaust gases leaving the tailpipe comply with the latest EU6c emissions standards.
Do petrol particulate filters need maintenance?
You don’t need to worry about maintaining your car’s petrol particulate filter. Unlike diesel particulate filters, which tend to clog up over time, PPFs work efficiently thanks to the naturally high operating temperatures of petrol engines.
The electronic control unit in some cars will monitor the status of the filter to detect when soot needs burning and automatically increase the exhaust gas temperature to achieve this.
How to clear a petrol particulate filter
It’s important to emphasise that the PPF should look after itself without intervention.
However, if you’ve noticed a warning light telling you the filter is full, try the following tips:
Drive at a high RPM - Increase the engine revs by dropping down a gear.
Motorway driving - Incorporate motorway driving into your routine.
Use a fuel additive - Use a specialist fuel additive to help clear the PPF.
Avoid idling - Prolonged idling leads to increased particulate buildup.
Can you remove a petrol particulate filter?
Removing a petrol particulate filter is technically possible - but that doesn’t mean you should.
PPFs ensure vehicles meet the required emissions standards, so tampering with the filter could leave you in legal hot water if discovered. Removing the PPF could also cause your car to fail its MOT due to excessive emissions.
Find out why MOT tests include an exhaust emissions test.
Legal implications aside, it’s not as straightforward as simply removing the filter. You’d then have to adjust the engine control unit to prevent the missing PPF filters from flagging a fault code or forcing the vehicle into limp mode.
Some companies offer PPF deletion services, but this is usually for track cars, not road-legal vehicles.
What cars have petrol particulate filters?
PPFs are common in most petrol cars made since 2018. Brands like Volkswagen, BMW, Mercedes, Volvo, Ford and Audi all use them. Even high-performance supercars like some Porsche 911 and Ferrari F8 Tributo models have PPFs to meet emissions standards.
What is the difference between a DPF and a petrol particulate filter?
Both petrol and diesel particulate filters serve the same purpose, but DPFs require more maintenance because diesel engines run cooler, meaning they struggle to burn off trapped particles efficiently. Diesel cars need regular high-speed runs to keep the DPF clear, while petrol cars don’t have that issue.
Find out how to avoid DPF problems in this guide.
So, if you’re driving a petrol car with a PPF, you can relax - it’s quietly doing its job in the background, helping to keep emissions down with little to no effort on your part.
If you found this guide helpful, you might also like:
- Related topics:
- Exhaust Repairs
- How It Works
- Maintenance
Written by Ellie
Ellie is FixMyCar's content manager. She has over three years of experience writing about cars and regularly collaborates with automotive experts to provide trustworthy advice for drivers that is easy understand. Her work has been featured in Yahoo! Finance, iNews, The Daily Express and The Sun. She has a BA in English literature and an MA in creative writing from Durham University. Outside of work, Ellie follows F1 and eagerly awaits Ferrari's next era of dominance in the sport. She drives a Suzuki Swift.