Fuel gauge query
 

I know that when the fuel gauge is halfway between the "empty" position and the quarter mark, that I have around an eight of a tank left

As the tank on my CDT holds 65 litres, this means I have around 16 litres or roughly 3.5 gallons

As I'm getting around 42 mpg at the moment, I should be theoretically be good for just over 140 miles. Right?

What worries me is that sometime the low fuel warning will be on at this level, sometimes not. So, which do I trust? The needle or the light? (and if the latter, how much fuel do I have left?!)

TBH I would trust neither and fill the tank a bit more often.:)

If you really must run the car until the light comes on test it a few times. As soon as the light appears fill up to the top. Deduct the number of litres you put in to fill from 65 and thats what you had left. If you do that a few times you will get a rough idea of what the light and gauge are showing you.

Even then its a bit hit and miss. All pump cutoffs are not the same. All garage forecourts are not level. The car may not be loaded in the same way each time. All these will effect exact amount of fuel you get in.

I always fill mine up when it hits the quarter full mark and it usually takes pretty much nigh on 45 litres. This means I've got 20 litres left but also means that I just divide my mileage covered since last fill up by 10 to get an accurate mpg figure. I managed 520 miles on 1/4 tank/45 litres last time so this came out at 52 mpg.

After an "incident" in an LDV van southbound on the M1 when I ran out of fuel about 10 miles short of London Gateway services and the gauge was still showing just under 1/4 full, I tend not to trust fuel gauges anymore. I also don't want the in-tank fuel pump running without being covered with diesel.

I agree that it's a bit hit and miss, but need to wait until payday until I next fill up!!

Actually my maths would be well off in the first post - if I had 140 miles left on an eight of a tank, I'd be getting 1020 miles per tankful.... (I know it's good, but it's not that good!)

Reality is more like 580 miles at very best, so the eight would give me around 70 miles....

The Fuel Warning light comes on when you have 9 Litres of Fuel left.
If you have the message centre and the additional Fuel Warning sign comes on refill straight away as its about to go Glug Glug Stop!
Its always best to never let any fuel tank get this low.

No Message Centre I'm afraid...... :(

There is an aditional message? I get the "Low Fuel" warning symbol that appears when the orange light appears on the guage, but I wasn't aware there was a second warning. This is - obviously - because I don't let it fall much further when the little orange light comes on.

Very sensible Simon.
Yes on the Hi Line Message Centre there is an additional Warning Symbol,
basically saying feed me you Fool how many warning lights do you want!!http://www.the75andztclub.co.uk/foru...ons/icon10.gif