I drive a BMW 320d. As an ex-Shell employee I always look out for V-Power Diesel as I like its performance and cleanliness. For several months Shell have been capping their V-Power Diesel nozzles with a "Double Club Points" sticker, but last weekend they must have transferred the double points deal to their V-Power unleaded petrol nozzles, right next to the V-Power diesel nozzles on a multi-fuel pump. I stopped at an unfamiliar Shell garage in Andover, pulled the red and black (double points) nozzle and squirted just two litres of unleaded into my tank before I realised what I had done.

The tank had about 20 litres of V-Power Diesel in it already, so I filled it up completely with another 45 litres of V-Power diesel, making it around two litres of petrol in 67 litres of petrol/diesel mixture. I was ten minutes away from a meeting on a Sunday afternoon and I figured that, being less dense than diesel, the petrol would either float on the top and not get picked up by the inlet tube at the bottom of the tank, or would dissolve in or form an emulsion with the diesel at a low concentration and get consumed over time. After the meeting I drove 140 miles home with no apparent problems. What should I do now?