Focus TDCI mpg gauge question...

[Damian S]

Noticed this ever since I brought the car. Say, I reset the gauge before going to work. I drive to work at which point the mpg gauge reads 52mpgs after driving the 16 miles, for example. At home time I switch the ignition on (not start the engine) and flip to the mpg gauge, it now reads 40mpgs. ???

The trip computer seems to do this a lot. Almost like it is recalibrating for whatever reason. Interestingly though, it mainly does it after my journey to work. Even this morning, it read 51.8mpgs (averaged over the last 120 miles) yet at lunchtime I went out and it had dropped to 50.0 before I have even started the engine. ???

Im just curious as to why it decides to drop the mpg for no apparent reason.

btw I have calibrated the mpg gauge with a tank of fuel and it seems pretty accurate, it reads perhaps 1 mpg under the real figure.

[Damian S]

anyone

[Trooper2]

Because it needs a speed sensor signal to be as accurate as possible, no speed signal and it drops back to some default.