35 miles is the best I have done on 0 on the trip computer
Done over 40 after the '0' indication and regularly go beyond it. I reckon there is a fair bit of capacity spare. Did over 55 on my old Toledo V5 when I was late for a plane. It was either fill up and miss the plane or push it on and hope to make it (which I did but I was sweating all the way - not a comfortable journey at a consumption rate of 26 mpg).
I know its generally not advised to run the tank low due to pulling the crap out of the bottom of the tank but I'm fairly selective with diesel purchases and opt for Shell which ought to be fairly free of contaminants.
Ohhh.... Pushing it!
First time I saw '0' too I cacked it - It was still another 7 miles to the petrol station.