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A Guide to Fuel Additives

If you believe everything you read, fuel additives act as a magic potion, with an ability to transform a tired engine into a smooth operator. They cost from around £5 a bottle, and you just pour the liquid into your fuel tank.

Fuel additives claim to improve your car's economy, performance, or both - but do they really work?

Fuel additives are available for both petrol and diesel engines. The manufacturers claim a list of benefits, including: - Keeping your carburettors clean

- Keeping your injectors and intake valves clean

- Removing water from your fuel system

There's also other supplements that are designed to work directly on the catalytic converter and exhaust parts.

Basically, what you should expect to see is a car that runs smoother, with better fuel economy, better performance, lower emissions and a prolonged engine life. Sounds amazing right? Let's dig in to these claims.

How they work:

Always follow the instructions on the bottle, but in the majority of cases you just add the liquid into your fuel tank when you fill up at the pump. The additive dilutes into the fuel, which is why your tank needs to be at least half full. It then flows along the fuel lines through the pump, into your injectors or carburettor, and then into the combustion chamber, cleaning each part as it goes.

In general, these additives work best on older, high mileage engines that have either been neglected or missed out on regular maintenance. You're unlikely to see any benefit on a newer, well-maintained vehicle.

Additive types:

It's important to do your homework before using an additive, as there are different fuel additives for various fuels and purposes. A quick Google search will reveal the different types and the claimed benefits, or you can read the bottle if you're in a store.

If you live in a cold climate and run a diesel car, you can get additives that stop the diesel fuel in your tank from congealing, which can cause blockages in the fuel system. And if you're putting a car into storage, another fuel additive can help preserve the fuel so that the car is easily started when you come back to it.

An engine flush could also prove useful if you're trying to get a car that hasn't run in a long time back on the road, as it should loosen off any residues and crust that has built up in the fuel system over time.


While these additives do help in certain situations and with different engines, the additives you should be skeptical of are those that claim to improve fuel economy. Even with the best will in the world, the reality is that any savings you make in economy will be more than cancelled out by the price of the fuel additive in the first place.


The reality is that if you own a car that's less than 10 years old that has been well maintained, there really isn't any need to use any of these kind of additives, as the car's electronics and fuel system will be optimised to deliver the best mix of performance and efficiency in the first place. And if that's the case, it begs the question - if fuel additives are so good, why don't car makers recommend them? And why are they not commonly found at petrol stations across the country?

In reality, they sort of are. If you feel like your car could do with a bit of a boost, then a better value alternative than an additive could be to use a higher octane forecourt fuel than regular 95 octane. Even supermarket chains offer 99 octane fuel these days for a few pence more than regular petrol, and leading fuel retailers make grand claims about the effective 'cleaning' that high-octane fuels can achieve.

These fuels are a necessity for highly tuned sports cars, but some firms even offer higher octane diesel fuel, and running a tankful through a regular car won't do any damage, and may even give your car the boost it needs.


In conclusion, if you've just bought an old car with a sketchy maintenance history, or it seems as though it hasn't been looked after, then stick a bottle of Redex in the tank when you top up. Go for a long drive and it will clean the insides, though for extended fuel economy, the evidence is hard supporting it is quite hard to come by.

Alternatively, fill up with a tank of premium fuel, as these also contain extra additives that can have the exact same effect, and a kick to power!

But whether you're running premium or Redex, there's nothing better than just taking care of your car and getting it regularly serviced. If you want to book in for a service, give us a call or drop by: Brandon Garage Windsor Street Haverton Hill TS23 4EY

01642 564120 Special thanks to Matti from MWM Digital for helping with our blog.

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