Has this happened to you?
There you are driving along and you glance at the petrol gauge. Oops the fuel gauge says it is dangerously close to empty!
Now I really want to get to work before I am late and all the petrol stations have queues a mile long (well almost!) so I decide to carry on and buy some petrol later on in the day.
Needless to say I forget. With every mile I take I am pushing my luck and promising myself that I will get more petrol at the next garage. At a guess I think I have travelled another 15 miles or so until I have topped the tank up.