Audi will fit its 2011 A4, A5 and Q5 TDI diesel models with a misfuelling device to prevent drivers accidentally filling them with petrol.
The fuel tank's 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.
This latest advance will be of particular interest to companies running vehicle fleets, but it will also provide reassurance for private customers making the switch from petrol, and those who aren’t the sole user of their car.
The newly equipped models in the A4, A5 and Q5 family will be joined by further Audi models in the near future as the system is gradually rolled out.