Fuel Tank mileage range - C5 2.2 HDI 51 plate

jimleshed · Post by **jimleshed** » 03 Sep 2010, 10:38

Anyone know how this works?
It confuses me....

MPG is easy, I know how it does that.

The 2 MPGs (trip 1 and 2) can be used to work some sort of average for tank range - simple.

But....

Why, when I am sitting in a traffic queue does the tank range increase, while the MPG goes down? Its always done it, ever since I got it a year ago. Does not matter if the tank is full or near empty, if I sit in a traffic queue the miles left in the tank increases. I was stuck in a bit hold up last night, and watched the range slowly tick up by about 35 miles, while the MPG dropped steadily..... any thoughts, or shall I just put this down to weird Citroén software?

Confused of Somerset...

Post by **myglaren** » 03 Sep 2010, 11:12

Logically, if you are stood still burning fuel both your MPG will drop (0mpg while stationary) and the range as you are consuming the fuel from the tank without going anywhere.

What the software probably does is estimate the range on the fuel remaining based on your average consumption and current consumption, disregarding the fact that progress is zero.

Mine doesn't work, will have to see what the daughter's SAAB does.

mooseshaver · Post by **mooseshaver** » 03 Sep 2010, 13:04

From what I remember from the manual, the range is based on the last ten minutes of driving.

jimleshed · Post by **jimleshed** » 03 Sep 2010, 13:17

Hmmm...I didnt think to look in the manual! I'll dig it out later and have a gander.

Its only idle curiosity anyway, I'm not overly concerned! I know that whatever the range says it is, I wont believe it....I never let the car get below 1/4 full - after it ran out of fuel while still saying it had 1/8 tank and no low fuel warning on!

Its nice to have a car with character....

mooseshaver · Post by **mooseshaver** » 03 Sep 2010, 13:35

Ran out of fuel? I wodner if you can calibrate fuel tanks?
Both my C5s have had acuarate tanks.
My Saxo and the C15 vans I used to drive were not so good.

jimleshed · Post by **jimleshed** » 03 Sep 2010, 15:03

Mooseshaver, you're right. I checked in my manual.

Its a combination of both MPGs with a last 10 minutes average. So I guess if I sat still long enough (11mins+) it would rise for a bit, then drop off rapidly!

Strange, my first assumption was that it was a Citroén quirke...

JLS

DickieG · Post by **DickieG** » 03 Sep 2010, 18:31

mooseshaver wrote:Ran out of fuel? I wodner if you can calibrate fuel tanks?

I know it can be done on Picasso's as I have done it myself but I don't know of other models.

cachaciero · Post by **cachaciero** » 03 Sep 2010, 21:07

mooseshaver wrote:Ran out of fuel? I wodner if you can calibrate fuel tanks?

Yes I believe you can, I seem to remember there are a couple places under the BSI menu of a Lexia which allow calibration.

cachaciero

jimleshed · Post by **jimleshed** » 04 Sep 2010, 17:26

Ooooh....perhaps I'll give that a go. I guess it needs to be done when the tank is either brimmed or empty. Next time I feel in the mood I'll dig out the Lexia and have a look!
Cheers

jimleshed · Post by **jimleshed** » 07 Nov 2010, 19:12

Just out of interest, the system must use the method MyGlaren put forward. It ignores current MPH, and averages the two MPGs plus your current usage. So at tickover you are not using much fuel, it just ignores the fact that you are not moving...

I've just sat in the car after a long trip (47 minutes driving) and watched the Tank range increase from 531 Miles to 646 miles, while sitting still for 13 minutes with the engine running. So the 10 minutes MPG average stated in the handbook is not exactly right.....well, it might be correct, as long as you are not stationary.....
JLS

Citroenmad · Post by **Citroenmad** » 07 Nov 2010, 20:33

If im sitting in stationary traffic my miles to empty figure goes down. If ive just set off with a cold engine the miles drops quite quickly, since the MPG is much lower, but it soon comes back up once running warm and economically.