even with miles till empty enabled the car is still going to guess as it works it out using the average MPG, which can so easily change.
Given that the light comes on when you've got 8l left (can be changed, and it's more for the V6) you'll have about 1 1/2 gallons of fuel left. You need to keep in mind, that that last 8l is going to contain all the dregs at the bottom of the tank (which the filter will filter out) but a diesel engine isn't the same as a petrol (obvioulsy) as in if you run out you can't just walk to the petrol station and put more in the tank, and empty diesel engine needs to be purged of any air that's been drawn in when the tank went dry.
