Car Clinic: After clearing petrol out of my diesel car's fuel system, should I pay for optional additive?

Q. When I put petrol in my diesel Audi A5, Fuel Doctor drained the tank. I declined to pay £20 for an additive to prevent “dangerous fumes in the tank” affecting the engine management system. Was this necessary?

RT, Norfolk

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A. We spoke to Fuel Doctor (0845 4590 000), which offers mis-fuelling remedies. It was baffled by talk of “dangerous fumes” and would be happy to discuss your issue.

It said an additive is available for about £20 that helps to lubricate the seals (around the injectors and suchlike), but is not vital, usually being recommended when fuel has got into a running engine.

If you had the fuel drained before driving the car (so avoiding damage to the fuel pump and injectors), you were right to decline the charge.

Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory — read more from Dave here.

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