Varying mpg according to the computer?
I've had a 1.9 JTDm 159 now for 3 months, and so far I've racked up about 5,000 miles.
I've noticed that according to "Trip A", my average mpg is about 37.5 - far from good, but not as bad as I was expecting given some of the comments on this site. Trip A has not been reset since new, so covers all the mileage done in the car in total.
Every time I fill up I reset "Trip B", so I can see what my most recent mpg is like - I'm aware that I should see it start to improve a little as the engine wear in.
However, recently, I've noticed something very strange happening. I drive the same way into work each day - and my trip involved a long stretch of motorway with a very slight slope downwards. Normall when travelling at, ahem, 70 mph (well, perhaps 80...) on this stretch, I get current mpg around 55-60. However, on the odd occasion, on the same stretch I get mpg of 25. The decrease seems to bear no correlation to the weather conditions or anything else, and I always seem toget about the same total miles out of a full tank, so I'm happy that "real" mpg hasnt reduced, so it must be the trip computer?
Has anyone else experienced this> It doesnt really matter I guess, but it does make the average mpg readouts artificially low, meaning I'll never get a true idea of what I'm getting?