Fuel for thought: should you embrace the additive?

What are fuel additives?

Fuel additives are products that you add to the petrol or diesel you put into your car with the aim of improving its performance.

They can cost as little as a fiver, are widely available in car parts stores, and just need to be added to your petrol or diesel tank. They have various stated uses, including cleaning your engine, lubricating it, reducing corrosion, improving fuel economy and increasing the octane rating of the fuel you're using, which helps prevent a problem called engine knocking.

However, manufacturers don't tend to recommend them – and consumer research suggests they may not be all they're cracked up to be. So should you bother with them?

Do fuel additives work?

It depends what you want them to do. Independent tests by consumer group Which? found that fuel additives don't increase fuel efficiency or improve engine performance. Additives that claimed to increase the fuel's octane rating were less effective than premium unleaded. If there is a slight improvement, it's offset by the cost of the additive.

However, there are some things that fuel additives can do, including:

Act as a lead replacement. Lead in petrol wasn't all bad: it raised its octane rating and protected the engine from wear and tear. Leaded petrol is now banned, so if you have an older petrol car that was designed to use leaded fuel, it might need a lead substitute if it can't run on unleaded.

Help diesel engines run smoothly in the cold. These additives stop the fuel congealing at sub-zero temperatures and blocking the system.

Help keep the engine in good condition if you're planning not to use the car for a while. Fuel sitting around can start to corrode the engine or degrade and gunk it up with deposits.

What can I do instead to keep my engine running smoothly?

Additives are usually intended for cars with a lot of miles on the clock which may not have been maintained as well as they could have been. If your car is less than ten years old and in good condition, they’re unlikely to have much effect. These days, your car's electronics and fuel systems are designed to optimise the engine's performance and efficiency anyway. The best way to keep it in good condition is to look after it and maintain and service it properly.

Higher octane petrol or premium diesel are a better purchase than fuel cleaner additives – they may have some engine cleaning benefits. An engine flush to remove debris from the fuel system is a good idea if you are restoring a car that has been out of use for a few years.

If you do want to use a fuel additive, make sure it's suitable for your car's engine and fuel system, and for the job you want it to do.

If you think your engine might not be working at its best, or you want some advice on looking after it, car dealers Carwise Group carry out car servicing and repairs too so can help with anything you'd like us to look at. Of course, we also sell a huge range of used cars at our dealerships in Maidstone, Harlow and Dunstable – you can see all our stock on our website, and then call us at whichever dealership is most convenient for you to book a test drive.