Audi has developed a new fuel filler cap to stop owners accidently filling their diesel models with petrol.
Audi A4, A5 and Q5 TDI models for the 2011 model year will be the first to benefit from the new system.
The fuel filler neck has been redesigned to incorporate contact points that open an internal fuel flap only when the larger diesel pump nozzle applies pressure on them.
The smaller diameter petrol nozzles do not make contact, ensuring that the filler flap remains closed to prevent access to the reservoir.
Instances of misfuelling have risen significantly in recent years creating inconvenient and potentially expensive consequences.
Audi believes this is due to the increased refinement of diesel models which has seen them run nearly as smoothly and quietly as their petrol counterparts.