I drive a Renault Grand Scenic, registered in June 2010, with a diesel engine. Having two Labradors I find the vehicle more than satisfactory. My problem started when I visited my local Tesco Fuel Station to avail myself of a 5p off voucher due to expire the following day.

I put 37 litres of diesel into my tank and drove away. No problem with local driving after the tank was topped up until five days later when driving the 10 miles to home. After about two miles there was a metallic fluttering which suddenly stopped.

As I approached my home the metallic noise got louder and I was pleased to pull onto the drive and switch the engine off. As the car is still under warranty, the next day I was able to get AA assistance to take my vehicle to my local Renault dealer.

Imagine my surprise when the local dealer (Sutton Park) told me there is petrol in the diesel tank. When I called at Tesco, the vehicle had about a quarter of a tank of diesel. The ticket from Tesco clearly shows 37 litres of diesel being paid for. Tesco told me this afternoon that samples taken today show no contamination of the diesel. They also state that no other complaints have been received. Their engineers have been requested to inspect the tanks but this will not be for another 48 to 72 hours.

I am at a loss as to how it took five days of local driving before affecting the engine and how can I prove Tesco is at fault? Sutton Park has given me samples of the fuel taken from the tank and one of the samples I have given to Tesco. I wonder if you could throw some light onto the petrol into diesel tanks issue, inasmuch as how long is it before the contamination is realised by the engine?

Also how can I tell whether the dealership is telling the truth to avoid possible warranty work? The dealership is looking to me to settle the bill, which, initially is just under £300.