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

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.

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