You may not realise it immediately, but petrol engine cleaners can be the healthiest things to use when you’re achieving high miles. Of course, good engine oil is even more 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.
Petrol engine cleaners are beneficial for a whole load of things. Because they help clean an engine, this simply means the heart of your car can reduce its emissions and improve its MPG slightly.
The best bit? You don’t need to be an experienced mechanic in order to use it. Petrol engine cleaners simply work by inserting it 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 as diesel engine cleaners.
The best petrol engine cleaners 2024 at a glance:
Best petrol engine cleaner: STP Ultra 5-in-1 Petrol System Cleaner 400ml – Buy from Amazon.
Editor’s pick: Wynn’s Formula Gold Petrol System Cleaner – Buy from Amazon.
Best for catalytic converters and exhausts: Cataclean Complete Fuel and Exhaust Cleaner – Buy from Amazon.
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 than just the injectors and give other components a clean as well.
The best petrol engine cleaners 2024
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
- Has to be regularly used at every fuel refill
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
- Isn't as good value per litre as some others
Best for catalytic converters and exhausts
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
FAQs and things to remember with petrol engine cleaners
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.
How will I know when it’s time to try some petrol injector cleaner?
The signs that you’ll need petrol or indeed 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.
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.
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.
Aaron Hussain is a commercial content writer at Bauer Media writing for Parkers and CAR. He is obsessed with classic cars and anything with a fascinating story to tell.
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