What causes carbon build up in engines?

All internal combustion engines (ICE) no matter whether petrol, diesel, LPG, methane, hybrid, or any other hydrocarbon all create carbon build up as a natural product of burning fuel.

Book Your Carbon Clean Today
Which? Trusted Trader Logo

Reviews For our Carbon Cleaning Services

Gary Simpson profile picture
Gary Simpson
1 week ago
Today Adrian from F5 Carbon7 DPF Clean came to de carbonise my xc60 he arrived bang on time he was very courteous and explained in great detail what the process was .
He set up within 5 minutes and went on to the diagnostics and talked me through what was coming up after a reset all was clear. It took about 1 hour in total great job well happy would definitely recommend Adrian well mannered gentleman.
Emils Matulis profile picture
Emils Matulis
2 weeks ago
Called for one service, but gentlemen helped diagnose the real problem and as well explain how to fix it!

Leon has great knowledge! Would recommend!
Will use in future!
Caroline Muscroft profile picture
Caroline Muscroft
4 weeks ago
Weve gone away to scarbrough on holiday and my dpf was blocked and not running properly. Messaged and came out to us the next day! Brilliant service thankyou so much! Will be booking in for the carbon clean next
Craig Harmieson profile picture
Craig Harmieson
4 weeks ago
Amazing service, didnt expect too much but totally blew mind, performance was increased, not much but I'd recently had a new turbo, so didnt expect much, as for mpg, I was expecting afew mpg here or there, but in truth it blew my mind, I have a 2005 mondeo st estate with 162k on the clock, and it went from 45.4 mpg on motorways to 68.8, posted video as proof, should highly recommend
Emma Valentine profile picture
Emma Valentine
1 month ago
Couldn’t ask for better service. Had a carbon clean done this week on my partner’s Astra. Adrian responded very quickly to my initial query and got us booked in for the next day. He was very thorough and explained everything that I wasn’t sure of (my knowledge on cars is awful). He provided the fault codes and the live engine data and gave great advice about how to fix the current issue we were having with our car. The car runs very smoothly and is finally lovely to drive again, wish we’d done this sooner. He was very friendly & polite which put any worries I had at rest. I wouldn’t go anywhere else. Thank you so much!
Seagrave Media profile picture
Seagrave Media
1 month ago
"I recently had F5 Engine Carbon Clean work on my three vehicles—a 2012 BMW X1, 2007 Jaguar XJ, and 2005 Audi TT—and the results are superb.
What really sets them apart is the comprehensive diagnostic work they carry out as part of the service. On two of my cars, the diagnostics highlighted a couple of underlying issues that I was completely unaware of. Because these were caught early, I was able to get them resolved alongside the carbon clean, which has made a massive difference to the overall performance.
All three cars now idle more quietly, feel sharper, and pull much more smoothly. It’s rare to find a service that combines deep technical knowledge with such tangible results. Professional, thorough, and highly recommended!"
Andrew Bailey profile picture
Andrew Bailey
1 month ago
Highly recommend!!
Excellent service, Adrian turned up on time, had the carbon clean and my car was diagnosed with a DPF issue so had a follow up appointment by Leon to sort out the issue and as I said before the car is much improved MPG seems back to normal and the car is running great.
Many thanks ????????
Charlie Stokes profile picture
Charlie Stokes
1 month ago
Steve came out to give our DPF a full clean on our bmw 2 series the before and after results are incredible. More power better MPG and overall the car feels way better to drive. He showed us the before and after statistics. We are definitely getting him back to do a carbon clean
Amy Fryer-skelham profile picture
Amy Fryer-skelham
1 month ago
Our 3rd car being done by Adrian and always impresses us with the results . Very happy and will be lining number 4 up very soon
Ben Castle profile picture
Ben Castle
2 months ago
Highly recommend this company.

Van was very sluggish and noisy so thought I would try a carbon clean and diagnostics.

Adrian was very quick to respond to my enquiry and managed to fit me in the same week. Adrian was incredibly knowledgeable and ran through the diagnostics with me and answered any questions I had. Carbon clean was quick and effective.
After the carbon clean the van drove a lot better and pulled through all gears very smoothly.
Well worth doing.
Adam Brown profile picture
Adam Brown
2 months ago
I rang Adrian after using him in the past and he got me booked in really quick, came out with constant updates on arrival time so didn’t have to sit around waiting. Did all the checks on the car then explained everything as it was being done, didn’t mind answering any questions asked. Mentioned a slight vibration and after it was all done the vibration was almost non existent sounded loads better and was driving in my opinion better. Really good job was very pleased and top man Thanks
Tim Ward profile picture
Tim Ward
2 months ago
All round a very impressive service.There is a noticeable improvement in my 100k mile diesel, it runs more smoothly and hopefully will have a better mpg.
Adrian also took time to examine a number of engine fault codes, listing them for me for further investigations.
Thank you!

Where does carbon build up come from?

When an engine is new, it typically runs smoothly and quietly, delivers good fuel economy, and produces low emissions. At this stage, carbon build up in the engine is minimal because combustion is clean and efficient.

Over time, this changes. In many vehicles, carbon build up can begin as early as 10,000 miles, particularly in modern petrol and diesel engines that rely on complex emissions control systems and are often used for short journeys.

All internal combustion engines create carbon as a natural result of burning fuel. When combustion is not perfect, known as incomplete combustion, unwanted by-products are produced.

Book Your Carbon Clean Today
C8H18 + Air (mainly N2 + O2) → CO2 + H2O + CO + C  + NOx

This is an example of incomplete combustion of octane. Alongside carbon dioxide and water, it produces carbon monoxide, solid carbon particles (soot), and nitrogen oxides. The ratio of these by-products varies depending on driving style, engine condition, fuel quality, and temperature.

Note the ‘bad stuff’ in orange.

How carbon build up affects engine performance

As carbon build up gathers inside the engine, it interferes with normal airflow and fuel delivery. The engine gradually loses the smooth, balanced running it once had and may begin to feel lumpy, uneven, or sluggish.

To compensate, the engine injects more fuel just to keep running. This is known as running rich. As this continues:

  • Fuel economy drops
  • The engine becomes noisier
  • Performance feels less responsive
carbon build up

This cycle explains what causes carbon build-up in an engine to get worse over time. Dirty combustion creates more deposits, which then create even dirtier combustion.

Book Your Carbon Clean Today

Emissions & MOT failures

When an engine runs rich, carbon build up causes higher emissions. Levels of carbon monoxide and carbon particles increase, which can eventually result in an MOT emissions failure.

This is especially common with carbon build up in diesel engines, where soot forms more readily due to the way diesel fuel burns.

Wear & component damage

Carbon buildup does not only affect emissions. Uneven combustion increases vibration within the engine, placing extra strain on components. Over time, this can accelerate wear on:

  • Fuel injectors
  • Engine mounts
  • Clutches and flywheels
Book Your Carbon Clean Today

Where carbon build up collects

Carbon deposits commonly gather in components such as:

  • EGR valves and EGR systems
  • Inlet manifolds
  • Intake ports and valves

These restrictions further reduce airflow, making the problem worse and accelerating carbon build-up.

carbon build up

Why is carbon build up more of a problem now?

Older engines were far simpler. Most unwanted combustion by-products were expelled directly through the exhaust, so carbon build up inside the engine was less noticeable.

To reduce emissions, modern vehicles are designed to trap and reuse exhaust gases rather than release them. Systems such as EGR valves, DPFs, catalytic converters, and GPFs prioritise keeping soot within the vehicle. While this benefits the environment, it also makes carbon buildup in petrol and diesel engines far more common.

Book Your Carbon Clean Today
What causes carbon build up in engine

Why carbon build up cleaning matters

Once carbon build up starts, combustion becomes less efficient, emissions rise, and deposits accumulate faster. Without carbon build up cleaning, this cycle continues, increasing the risk of EGR faults, inlet manifold blockages, DPF issues, and long-term engine wear.

Even with cleaner fuels and modern additives, carbon build up does not disappear completely. Modern engines simply create the conditions for it to form.

The good news…

Regular engine carbon build-up cleaning can help break this cycle, restoring smoother running, improving efficiency, and reducing emissions. Thankfully, this is something we can help with.

F5ECC Team
Book Your Carbon Clean Today