Winter diesel always means less MPG. Usually starts in mid November and ends early April.

And how are you getting 50 mpg from a 2.0 130 PS Mondeo. Ours did a true 38 mpg overall for the 3 years we had it, the best we ever saw was 48 mpg on a holiday trip. Suggest you carry out a few tank to tank fill ups and ignore the computer on the dash, think you will be in for a shock.

I don't thing that 50 mpg is overly high for a 2.0. common rail engine.

From personal experience I know it is unbelievable from a Mk 3 Mondeo, as I said we had one 3 years so shoul;d know. I averaged 48 mpg over the 5 years I had a BMW 118D but the engine in that was way more advanced than the old Mondeo lump. We "only" get 51 mpg overall out of a Kia Ceed 1.6 CRDi which we think is brilliant since the Focus 1.6 TDCi that we had before it only averaged the mid 40's.

Most people simply quote the figures recorded by the display on the dash but most tell more lies than a politician. The BMW one used to say 53 mpg instead of the calculated 48 mpg, my current Seat Leon says 50 mpg but the truth is closer to 45 mpg when calculated.