I've owned my mondeo st tdci for almost a year now and as a rule I've always used premium fuel in all my cars. The car is in great shape with no mechanical issues and is standard apart from h&r lowering springs.

This is my first diesel car and a few months ago I was caught short (out in the middle of nowhere) and had to fill up at Morrisons, which I wasn't keen on doing, but needs must btw I had ¼ of a tank left, but I don't like to run the tank into the red.

I got about 5 miles down the road and for the first time in my ownership the engine went into limp mode! So I turned it off and started it up and all was fine for a few miles. My car went into limp mode 4 times during that tank of supermarket fuel!

I fill up my car to the top once a week and it's in constant use up and down the motorway to and from work. So as an experiment I filled up with supermarket fuel once a month over the last 3 months. Tesco, sainsburys and Morrisons in that order. Every time it had supermarket fuel in, it would go into limp mode at least twice during that tank of fuel. Tesco's being the worse with the engine going into limp mode 6 times.

I know it's not the most scientific experiment but I'd like to know what people's experiences are with supermarket fuel. If my experience is anything to go by its pretty aweful stuff! Personally I'm starting to think supermarket fuel is responsible for the majority of diesel injector, pump failure etc.

Anyway, back to running the mondeo on the good stuff and it hasn't missed a beat