Thread: D4 Distance to Empty Accuracy

That's a really good question PJJ. I had noticed the same myself. I now have just over 10k up on my D4 3.0 SDV6 and it looks like the range is about 100 KM less than my D3. I also notice that in the manual it states that the D4 will hold a minimum reserve in the tank and will shut down the engine before it actually starves of fuel. So I have put this down to the fact that the 5 or 6 litres or so that it is allowing for makes the difference.

Is the D to E consistent with how much is left based on how much you get in to the tank when filling?
There's quite a bit in a few threads about how the trip meter is optimistic about the average economy. I've actually found the opposite with respect to finding myself filling up before I need to based on the suggested D to E.
I also noticed once, after my better half got carried away driving in Sport mode for 400km around town, that the trip meter said her average fuel use was 19 l/100km... But I only got 60 litres into the car... ie 15 per 100, which I can believe.
In summary, I don't think the instant fuel consumption curve is normally distributed, and can be skewed either way depending on how you drive (evidenced by my wife and her lead foot!). So if that's how the car estimates the mean consumption, rather than just from total fuel by distance, it's very likely to be wrong, and so will the estimated distance to empty...
Discuss!

I've been logging the D to E both before I refill and after along odometer / trip, Average Fuel Consumption Rate and the volume of fuel added (subtracting this from the stated capacity to give fuel left in the tank before refilling). My observations have been that the D to E is derived from some "Recent" average fuel consumption rather than the "Average" since the trip computer (A, B or Auto) was reset. I base this on what happens when I leave Melbourne with half a tank and hit the Princes Highway. The D to E substancially increases as I get a hundred plus K's at highway cruising. The reverse happens when I get back to Melbourne. The D to E might show 200km but after doing 30km in traffic the following day it's down to 100km. I think it's quite logical to use the "Recent" average consumption rate to give a more realistic D to E.
Now moving on to the litres/100km. I rearly get the displayed Average to correspond with the calculated. The calculated is always higher than the displayed. I have kept the "B" trip untouched since new so it gives me the long term Average and vary between "A" and "Auto" for driving use. I've found Auto easy to use and to add subsequent "Trips" easy. You have until the next switch off to add them.

Originally Posted by rufusking

My observations have been that the D to E is derived from some "Recent" average fuel consumption rather than the "Average" since the trip computer (A, B or Auto) was reset.

Some vehicles certainly do that. I would have thought that they all did. It would definitely be much more useful if they work as you described.

IIRC, the handbook states that the low fuel light is triggered once there is a specific volume of fuel left in the tank (can't remember the figure - 8 ltrs?). This automatically sets the display to D to E mode, and I've always found a different figure being displayed, depending on how I've been driving the last 100km or so. So yes, I think it's based on some average metric.

On a side note, the Statesman I've had as a loan car for the last week displays a D to E figure that can vary between 380km and 540km within 20km or so!!

Cheers,

Gordon

Thanks for all the replies, but where does that all leave us? On a good trip in the D3 (economical like), it wasn't uncommon for me to get in excess of 900klms before filling up. The manual states that the fuel tank capacity is 82ltrs, but I have put 92 in it a few times.( it was still running)But the D4 seems to be a lot more conservative on the D to E readout & if the engine will shutdown before it runs out of fuel, does that mean I now have effectively less range than the D3? Seams crazy to me!

Phil

Just thinking more about this -
What is the biggest fill that anyone has done in a D4? At this time I have only managed 74 ltrs With the fuel light on & D to E of 80klms.
Also, if the motor cuts out on low fuel, what is the procedure for a restart?
This is going to drive me Crazy

Phil

Interesting read, I just returned from a trip up to the snow with a mate of mine in a D3 and me in my D4.

His L/100km figures were a couple of liters worse than mine the whole way on the computer but we both put it in exactly the same amount of fuel on return to home. we convoyed the whole way so exactly same distance etc. We both had 28L left in the tank and my D to E was 200km and his was 410km.

My L/100km figure was 8.5/100 according to the car but actual calculated by me was 11.5L/100km, way off.