I like to keep 1/4 of a tank, but not always possible at the price of derv nowadays.
I never like it going into the reserve, although I do on occasion run on the reserve, knowing I have a good 60 or so miles on it.
I put £15.00 Biodiesel in the other day, took it from just above the reserve to nearly half full, was made up. I find like yourself Pete, the more fuel I see on my gauge, the more driving I do and therefore the quicker I use it.
if you let it go too low, you risk pulling the crap in the tank thru the engine..
That theory isnt true matey... what do you think you're fuel filter is for?? Not to mention the fact on most fuel tanks, the pipe is understandably at the bottom of the fuel tank, so any "crap" will go through the system whether its high or low anyway.