You may not realise it immediately, but a petrol engine cleaner can be the healthiest thing for your engine when you’re achieving high miles. Of course, good engine oil is essential, but keeping the petrol system clean is equally so. Over time, carbon deposits build up in an engine, requiring treatment with a good fuel additive. If untreated, it can lead to blocking important components, including the injectors.
The best bit? You don’t need to be an experienced mechanic in order to use a petrol engine cleaner. They simply work by inserting them with the fuel and running the engine normally. This means you can simultaneously get on with your everyday life without sacrificing the use of your vehicle. The principle is exactly the same for diesel engine cleaners.
The best petrol engine cleaners 2025 at a glance
Nevertheless, petrol engine cleaners are worth it when you need to make your engine run that little bit more smoothly, and because they’re more comprehensive than petrol and diesel injector cleaners, they can tackle a little bit more and give other components a clean as well. If you’re wanting to be a little more thorough then we suggest a car degreaser for your engine bay.
Why use a petrol engine cleaner?
Engine cleaner is a chemical cleaning agent that can be used to remove dirt, debris, and carbon deposits from the inside of your engine. They’re great for maintaining the health of your engine, which can provide other benefits such as greater performance and improved fuel economy. If you’re engine is running poorly then it could do with a good clean.
How do petrol engine cleaners work?
Engine cleaners typically contain solvents and detergents to help clean fuel residue and carbon deposits in the fuel system, injectors, and combustion chamber leaving your engine to work more efficiently. You insert them into the fuel tank during refuelling, and then they circulate through the fuel lines dissolving and dispersing any unwanted residue which can be flushed out through the combustion and exhaust process.
What to consider when purchasing an engine cleaner
There are a number of things to consider when purchasing an engine cleaner including:
Is it safe for my engine? Generally, yes. It is important to make sure that the product you’re buying is compatible with your engine, and then be sure to read the instructions carefully to make sure not to use too much product. Aside from that you shouldn’t really have much of a problem – though we would recommend caution when using petrol engine cleaner on older engines.
Will it affect my warranty? In some cases adding engine cleaner into the fuel system can affect your car’s warranty. Before purchasing a petrol engine cleaner we would recommend you check with your manufacturer or local dealer to be clear on warranty issues.
How often should I use it? That depends on the product itself. Some engine cleaners require you to insert the product into your car during every fuel stop, whereas others will recommend regular intervals of a couple of months. You might also find some products that mention a recommended mileage interval before adding another shot.
Is it easy to apply? Yes, they are fairly easy to use. In fact, you might find it more difficult than setting up a dash cam. For most petrol engine cleaners you simply have to pour them into the fuel tank in the same way you’d fuel your car.
The best petrol engine cleaners 2025
Best petrol engine cleaner
Realistically, there is only a subtle difference between each product. So, we'd recommend the 5 in 1 in a heartbeat, as it should cover all bases that the others tackle individually, and give your injectors and other vital engine parts a good clean and flush.
Pros
- Multi-tasking cleaner that deals with all there is to clean
- Good value for money for a 5-in-1, compared to STP's individual cleaners
- Helps engines run smoothly and more cleanly
Cons
- Quite easy to get through 400ml in a tank
Editor's pick
It doesn't harm the catalytic converter, reduces hydrocarbon emissions, and helps to make the engine a bit smoother than what it might've been before you added in the additive. In terms of value for money, it sits at the more premium end of the price spectrum, but it's a very effective formula in treating a slightly dirty engine.
Pros
- Helps to reduce emissions and help with fuel consumption
- Doesn't need to be added to every tank of fuel (rather every 3,100 miles)
- Good value for money per usage
Cons
- Isn't as good value per 500ml as the brand's Xtreme petrol system cleaner
Best value petrol engine cleaner
The best part is that they are extremely good value for money. So, if you buy in bulk, that's over 1,000 miles of engine cleaning covered. But we recommend you apply this stuff to every tank to get the best out of it. It's especially useful to older fuel-injected cars which might be running a bit lumpy.
I can vouch for it myself as I use it regularly every time I fill up my Mercedes 230E, which has an older Bosch K-jet injection system. Suffice to say, the engine has never run rough during my ownership.
Aaron Hussain
Pros
- Great value for money at £5 per 250ml
- Choice of bottle sizes or 'shots'
- Helps keep older engines running sweetly (in continuous use)
Cons
- Not as comprehensive as STP's 5 in 1
Best for cars with EGR systems
One particular benefit is the seal cutter on the lid. As someone who has struggled to open the seal of a Redex bottle while other cars are queuing at the petrol station, this is hugely welcomed - and guaranteed a time saver.
Pros
- Seal cutter is useful and saves time when opening
- Helps clean a whole host of engine parts
- Helps clean EGR system, which is usually expensive to repair
Cons
- 325ml isn't the most generous offering, unlike competitors
Best petrol system additive
It was made in collaboration with the F1 team - presumably using some of the expertise from the engineers regarding the efficiency and concentration of the ingredients. It helps improve efficiency, MPG and power output if your fuel injectors are slightly dirty. And don't, for a second, believe in the 'Mercedes F1 performance' line. Your road car will not suddenly feel like Lewis Hamilton's 2021 car in qualifying mode.
Pros
- Comprehensive engine cleaner that deals with injectors to emissions
- Uses expertise from a well-known brand
- Designed for use in stop/start engines
Cons
- Isn't much different to other cleaners, despite branding
Best for catalytic converters and exhausts
Rrp: $30.36
Rrp: $30.36
It helps clean up the fuel lines, injectors, catalytic converters, EGR valves, as well as improve the essentials such as MPG and efficiency. You can even order a pack of up to six if you want to maintain your engine for around 18 months.
Pros
- Ideal for catalytic converters and exhaust systems
- Quite strong compared to the others
- You don't have to use it too often
Cons
- Usage instructions are very specific
Granted, keeping engines squeaky clean isn’t as thought-of as topping up on screenwash. But while we recommend you keep your petrol injectors and other components clean, just as you would with diesel injectors, there are instances where you won’t necessarily need to. A lot of premium fuels these days, such as Shell V-Power, will simultaneously act as an engine cleaner as well as a fuel for your vehicle. And if you use advanced fuels like that, you should be fine.
FAQs and things to remember with petrol engine cleaners
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When should I use a petrol injector cleaner?
The signs that you'll need petrol or diesel engine cleaners are a slight lack in performance, a fairly rough idle, or if the car is running higher exhaust emissions than it should be. Where petrol engine cleaners make a substantial difference, though, is with older petrol engines and those with higher miles. Retro/classic cars that run on E5 petrol and/or have older Bosch injection systems benefit massively from a good clean, as well as regular oil changes using a good set of engine flush.
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How much engine cleaner should I use?
It varies depending on which petrol engine cleaner you go for. Most engine cleaners come in a 500ml (or less) bottle which is used in one go. Some engine cleaners like Redex come in a 2-shot or 4-shot version so it's important to read the instructions before use. Another thing to consider is the usage interval - some engine cleaners will require you to empty the bottle with every fuel stop, while others will recommend you use them every few months. It's important to check the usage interval as this will inevitably have an effect on value for money. Lastly, you should be careful to add the engine cleaner to the correct amount of fuel, for example, Cataclean's 8 in 1 solution requires you to add it to 15 litres of fuel every three months.
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What if it doesn't work on my engine?
A simple flush clean can instantly make an engine feel smoother, and regularly using the stuff can help maintain its longevity. If, however, you've tried fuel injector cleaners and your engine is still feeling rough, then the problem may lie deeper. If you're lucky, you may just need to change your air filter. But you'll need a full diagnosis as a rough-running engine could mean it's time for a new set of injectors, spark plugs, or more.
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How long will it take until I notice the difference?
Truthfully, we can't give a concrete answer. It depends on the condition of your engine and which product you go for. But after a few bottles of regular-use cleaners, you should notice the idle of your engine is smoother than it was before. That's a sign that the injectors and other components are less blocked with carbon deposits, thanks to the additive clearing them away.
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