Car Clinic: Can additives reduce the pollution from a diesel car?

Car Clinic: Can additives reduce the pollution from a diesel car?

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Q. Can fuel additives or retrofitted devices make a diesel car less polluting? And will removing biofuel reduce NOx emissions?
MH, Wetherby, West Yorkshire

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A. It is possible to fit older vehicles with kit that will reduce gases to meet emissions standards, but it is financially viable only for commercial vehicles.

Most diesel contains an additive (premium fuels often have stronger ones, or you can add your own) that clean the engine, helping it to run more efficiently and thereby cutting emissions. UK diesel contains up to 7% biofuel, and under heavy load it can create more oxides of nitrogen (NOx), but the effect is negligible compared with that of poor maintenance or a harsh driving style.

Sunday Times Driving Car Clinic: Tim Shallcross, advance driving advice
Tim Shallcross used to train AA patrols to fix cars. Now he advises the Institute of Advanced Motoring — read more from Tim here.

Email your question to or write to Car Clinic, Driving, The Sunday Times, 1 London Bridge Street, London, SE1 9GF, with a daytime phone number, your address and as much detail about your car as possible. We can’t reply in person, so don’t send original documents or SAEs. Advice is given without legal responsibility.