mpg computer only averages last 1000km?

[R-P]

Hi all,

I've seen on many occasion that the mpg (actually l/100km) indicator can change pretty quickly, even though I NEVER reset it.
Does anyone know over how many km or miles it actually keeps track and calculates?

Example: I drove the car for over 50,000km, yet in a 300km trip I got it from 9.3l/100km (30.4mpg) to 8.9l/100km (31.7mpg). Even if I had been towed (...) that should have not made that much of an impact... (then only from 30.4 to 30.6mpg...)


Rough calculation shows that if I assume I used 8l/100km (35mpg) over 300km and add that to 9.3l/100km over 700km (=1000 minus 300), then I wind up with 8.9l/100km.
But the 8l/100km is just a guesstimation obviously...

[Bernard333]

I did not reset the average mpg trip on my 2003 V70 for the first seven thousand miles to see how closely it correlated with the mpg measured brim to brim over the same distance , its about 5 to 6% optomistic but did not reset . Now eight years on and a fault has developed and it resets itself often after 70 or 100 miles , its annoying but I think it would take more time than its worth trying to fix it . Its definitely a known fault as others have reported the same thing on the forum .