Originally Posted by BristolMotorSpeedway
2009 E90 320D (177)
Looking back at my previous posts in this thread, the overall average (never reset since new) was reading:
At 9500miles 57.6mpg
At 19200 miles 55.4 mpg, having just spent 5000 miles on winter tyres during a cold winter.
Now the car has covered 35500 miles and the overall average is back up to 57.6 mpg. So it looks like the last 16k miles or so have probably had an average around the 60 mpg mark.
The winter tyres have been back on for 3 weeks, and it is clear that consumption is a fair bit worse again, perhaps 5-10% off. Obviously the higher rolling resistance of the winter tyres makes a reasonably significant difference to consumption, as it can't be put down to cold weather so far.
I'm pretty sure the OBC remembers the last 9999 miles only, and then loops.