petrol. Now, you usually have the choice between standard and premium diesel but which should you go for? Modern diesels are king when it comes to fuel economy but can paying more per litre actually save you money?
The fuel manufacturers boast various claims for their premium fuels, mainly that they increase fuel economy and keep vital engine parts clean. Detergents in the fuel help to clean the engines injectors which fire the fuel into the combustion chamber at incredibly high pressure and their proper operation is vital for good performance and economy. As such, premium diesel could help keep injectors in good condition but most experts suggest that heavy deposits on injectors can only be removed with specialist sonic cleaning tools- something to be aware of with older vehicles.
Independent tests suggest that premium fuels have a small benefit in performance in high performance engines. Sadly these tests showed no major fuel economy benefit.