Alternative Fuels Fuel Additives

What is a fuel additive?

CheckFuelPrices Editorial Expert Written • 3 industry sources

Reviewed by Jonathan Mathews VERIFIED

LinkedIn Articles 5+ Yrs Peer Reviewed

A fuel additive is a chemical compound blended into petrol or diesel to improve its performance, cleanliness, or stability. All fuel sold in the UK contains additives by law, with branded and premium fuels typically using more advanced additive packages than standard grades.

What Fuel Additives Actually Do

Engine cleaning: Detergent additives remove carbon deposits from fuel injectors and intake valves, helping the engine run more efficiently over time. 2

Combustion improvement: Some additives raise the octane rating of petrol or the cetane rating of diesel, allowing fuel to burn more completely and reducing engine knock. 2

Corrosion and oxidation protection: Stabilisers and anti-corrosion additives prevent fuel from degrading in storage and protect metal components in the fuel system. 2

Additives Already in Your Fuel

Minimum legal requirements: UK fuel standards require all petrol and diesel to contain a minimum additive package. This ensures every litre you buy meets baseline quality and emissions standards. 2

Bioethanol as an additive: Standard E10 petrol contains up to 10% bioethanol, which is itself an additive blended to reduce carbon emissions from road transport. 3

Premium fuel packages: Branded premium fuels such as Shell V-Power and BP Ultimate contain higher concentrations of proprietary cleaning and performance additives beyond the legal minimum. 1

Aftermarket Additives You Buy Separately

Off-the-shelf products: Bottles of fuel additive sold in motor factors and supermarkets typically contain concentrated detergents or injector cleaners that you pour directly into your fuel tank.

Limited benefit for modern cars: Most modern engines run on fuel that already meets strict additive standards. Aftermarket additives offer marginal benefit unless you drive an older vehicle or have a specific engine issue.

Regulated formulations: Any fuel additive sold or used commercially in the UK must comply with government fuel quality regulations, so rogue or harmful formulations are controlled by law. 2

Choosing the Right Fuel for Your Car

Premium vs standard: If your car would benefit from a higher-additive fuel, the easiest option is choosing a branded premium grade rather than buying a separate additive product.

Compare prices before you fill up: Premium and standard fuel prices vary significantly between stations. CheckFuelPrices shows live prices at 4,000+ UK stations so you can find the best value near you. 1