Thread: How accurate is the computer?

I can remember watching it read "0 km" a few weeks ago when starting, then 5 minutes later it was reading "121 km".

Ok, I was parked overnight with the front facing downhill if that made any difference.

Before the longranger tank went in, i could fill to top and fit around 90 litres in, now I fill to top taking many minutes and the max I have managed to put in (combined tanks) is 198 litres (and it wasn't quite empty).

So far the max I have run with "0 km" showing is 87 km till first cough

Mine's the same. Had lots of scares thinking I'm on the brink of being out of fuel only to find there was 10 litres or so in the tank.

I think the carputer reads economy 1l/100km better than actual, but this would mean you'd have less fuel, not more. Go figure!

Originally Posted by gps-au

I can remember watching it read "0 km" a few weeks ago when starting, then 5 minutes later it was reading "121 km".

Ok, I was parked overnight with the front facing downhill if that made any difference.

This morning while crawling in traffic, going up or down hill made about 5km difference to the reading......... up = less, down = more....... so I gather the sensor is at the front of the tank........

I think that you are about right with the 5L="empty" guide, but remember the fuel pump uses the surrounding fuel to keep it cool. If you run it lower, you risk overheating the pump.

Hi DiscoSaffa, no there are two sensors.

Originally Posted by Bushwanderer

I think that you are about right with the 5L="empty" guide, but remember the fuel pump uses the surrounding fuel to keep it cool. If you run it lower, you risk overheating the pump.

Hi DiscoSaffa, no there are two sensors.

Two sensors...... interesting..... what about fuel take off? Not that one should be doing anything to hairy off road with an empty tank, but where is the fuel take off positioned in the tank?

With respect to the cooling, again interesting...... I tend to try and not run to lower than a quarter tank as a rule, sludge etc etc..... but every so often needs must..... you think they would warn you about something like this in the manual..... Blew a pump in my Flandy back in the UK, wonder if this is what killed it?

Hi Discosaffa, in most cases of fuel tanks, (whether they are in planes, boats, trains or cars) the "usuable" amount is usually going to be less than the total tank capacity.

In other words, there will usually be some fuel that cannot be accessed by the pump.

So, perhaps, you were very close to that unrecoverable amount when by sutracting the amount put in from the tank capacity, you found you had 5 litres.

Another point does arise, and that is that many service station pumps over-read (gives the business a little profit margin), so in fact you may have had slightly more than your calculated reserve

FWIW, for peace of mind, I like to have something on the gauge and so top up when convenient in regard to price etc

My carputer (V6 petrol) was saying 16kms, and when I filled it I put 80L in the tank! I was wetting myself as I was stuck in traffic just watching the carputer say 40km, 30km then 21km till empty and I had only travelled 400m! I don't risk it, get to eight Km's just stop and put fuel in.

The carputer works out range based on recent fuel consumption and fuel remaining. If you spend an hour idling in traffic then hit the freeway your fuel consumption (l / 100km) will drop and thus you will see your range increase. The reverse situation would see your range decrease much quicker than the distance you travel.

While the D3 has an 85l tank (or thereabouts, it does vary on models) the fuel warning comes on at I think 80km. A conservative 80km. Also note that you can, like most cars, get another 5-8l in if you trickle-fill till you see the fuel almost slop out of the filler.

The angle the car is parked at will make a difference to the fuel reading if the tank is partially full.

Cold cars use more fuel than warm ones so fuel consumption will drop as you move off and warm up, and range will increase.

Fuel consumption readouts are in my experience invariably optimistic, eg reporting 11/100 when in fact it is 11.5 or 12.

You don't ever want to run out of fuel on a modern car.