Distance to empty on Fiesta changes rapidly near end of tank

[robertwoodliff]

Have a '14 Ford Fiesta. Can get very confusing info from mpg read out if coming into London / large built up area if after a long run up from the south coast / free flowing roads .
It may go from showing 34 miles to tank empty to showing 6 in 3 miles ....... makes you think quick where the next fuel station is !

[oldtamiyaphile]

Most cars are designed this way. A lot will go from 50km DTE to -- at once.

Some cars like my Fiat report actual fuel level that can be ready via OBD. It's nice to know the exact % of fuel in the tank (which I've found to be quite accurate), but they don't want joe public to have that info and always refuel at 1% remaining.

[robertwoodliff]

Thanks for the reply.
Have you run the Fiat down to 0% and seen how far it will do " empty " ? The Fiesta managed several miles with 0 to empty !

[Nedlom]

I have a 2007 fiesta, which is of course much older, but I would imagine the ecu etc probably uses the same calculations or whatever.

The distance to empty is pretty accurate - with a few caveats.

The fuel sensor/ecu will quickly respond to a perceived drop in fuel level, but take much longer to respond to an increase. Example - driving along on a straight road DTE reads x, come to a roundabout the fuel sloshes around and the DTE starts to plumit. Stays low for the rest of the journey, but park up and come back half an hour later and DTE has jumped back up again.

I regularly drive on almost empty to save weight, and when this low on fuel even filling up at the pump it won't update until the ecu has been to sleep and reawoken.

Once I got cocky - car had been sitting overnight on level ground (very important!) showed a genuine 2 miles to empty. Cheapest fuel was 4 miles away - no bother, these things are always over cautious anyway... the last mile was walked with a jerry can in hand

As long as I start my journey with enough miles to go showing, I know I'll be good.

[jcp123]

My wife's van is like this. I can see a fast decline in DTE when a hill causes fuel level readings to drop, and it recovers super slowly if the fuel reading increases again. It's a programming quirk, not necessarily a defect.

[Fat Charlie]

Originally Posted by Nedlom

As long as I start my journey with enough miles to go showing, I know I'll be good.

As long as the leg you have to take is one where you can meet or beat your tank average. My town is 680 feet above sea level and for a long time I worked at sea level. My morning run was above the tank average, and my evening run was below. Going home, DTE wasn't in my favor.

As to accuracy, as long as we keep using a bobber on a lever in a horizontal tank to measure, that is going to be one vague reading. I love my UG with its calculated level.