i do the same, as a back up to my low fuel light. i just switch it back every once in a while to see if i've hit my next 4kml interval for servicing.I usually keep my odometer on trip too. I haven't switched it back in a while and really have no idea how many miles mine has on it. I guess I need to do that. Last time I checked it had 26,000 miles on the clock. That was several months ago. Probably due for an oil change.