Erratic Mpg Reading - Fiesta 2006 1.4 Tdci

Hi Guys and Gals,

I have owned my 2006 1.4 Diesel Fiesta for just shy of a year now.

I commute almost 100 miles a day in it on the motorway, and average around the 60MPG mark (I reset the counter on the first of the month).

Over the last few months I have noticed the average MPG start to slip. First to the mid 50s then the mid 40s. Something is obviously not right.

This morning on my way to work, the average MPG dropped dramatically (by about 10MPG) when going up a steep hill on the A31. Once the road leveled out the MPG continued to fall down to around 33MPG. Eventually it started to climb again ending around 38.

Driving home from work today, the counter started accelerating, 40, 45, 50, 55 by the time I got back it was about 58.

Any idea what would cause such a rapid change in MPG? As I mentioned, I reset the counter once a month (on the first) to keep track of my fuel usage over the month. So the average was being taken over the last 1,400 miles.

Full disclosure, the turbo has been whining for about 9 months now, think its finally giving out?

Thanks for any help.