I've only had the car 2 weeks and came embarrassingly close to calling out the AA on Sunday when my range to empty showed 10 miles with me being 20 miles from the nearest fuel station!  My own fault of course but the range did drop dramatically from when the warning first came up at 50 miles.  Anyway, I managed to nurse it to fill up and put in 47.25 litres - the manual shows the diesel tank to be only 47 litres so I must have been close to the limit.  The car drives fine now so I hope I didn't cause any damage by sucking up the last of the crud from the bottom of the tank to choke the fuel filter.  The car only has 8000 miles so shouldn't have too much dirt in there yet (fingers crossed). 

When I bought my car. On test drive the range showed zero miles. They said it would be fine, sort of laughing it off. I probably drove about 5 miles but at one point it started flashing.
I don't personally drive it that low but is good to know even at zero I may have a little left.
I'm unsure at the time what average mpg it was showing though so could have been very low and so it thought at that rate it wouldn't get far.

Yeh on my old Mk2 Focus the fuel light would come on at 50 miles, my short urban trips dropped that 50 pretty quickly,
That '50 miles' must be if you are cruising on the motorway running at peak efficiency.

When I picked up my 4 year old Focus ST last year I intended on filling it with premium fuel,
I ran it down to 0 and it took about 54.5 litres in a 55 litre tank, not sure whats in the pipes but when it says 0 I'm not risking it much further.
I try not to run it much lower than a quarter of a tank these days.

Yeah, I don't know how it calculates the miles to empty, based on historic driving pattern or actual conditions?  I say that because I was driving up a mountain and the range fell from 50 miles to 10 miles even though I only drove about 20.  Then coasting back down the mountain the range followed the number of miles driven even though I was using nearly no fuel.  Probably a mix of both.   Anyway, nice to know that there is at least 10 miles reserve when it says zero, not that I want to try it again.

I've hit 0 a few times.  Range is never accurate, I always brim it and reset the trip counter to watch the miles covered instead.  I can lose 20 miles of range just by parking for a few hours...   

Sure I did it in the Mk2 as well but I can only find a 7 mile picture...  

But the Mk3 Focus range was the worst by far!  The variable fuel light came on at 90 miles sometimes!  But even with 0 range, there was still plenty left as demonstrated here lol...  Got another 20 miles out of it and still only just managed to get 50 litres into the 53 litre tank!

They must have got it better on the Mk 4s, seeing as I got 47.25 ltr into a 47 ltr tank,either that or they are lying about the tank capacity.

6 minutes ago, south_bound said:

They must have got it better on the Mk 4s, seeing as I got 47.25 ltr into a 47 ltr tank,either that or they are lying about the tank capacity.

I reckon they got so many complaints about the Mk3 they've over compensated on the Mk4!  

Did you notice when the fuel light came on?  It used to be 50 miles on the Mk2.5.  But then went variable on the Mk3 which was useless.  

Also, do you know why the tank is so small on the Mk4?  How big is the AdBlue tank?  Wondering if it has to accommodate that...

5 minutes ago, south_bound said:

I got 47.25 ltr into a 47 ltr tank,either that or they are lying about the tank capacity.

the tank will be pretty accurate, the rest is in the pipe between the tank and filler, I also wouldn't trust what the pump says lol.