MY 03 WRX, 60 litre tank - low fuel light came on (9 litres left), did 35 miles to get to Optimax station but for the last half a mile the car was not pulling fully on a slight incline.

Anyway got 58 litres in on the refill. Motto - 2 litres left is not enough with a bit of gradient, pitch and/or dive. Will try to keep it to 4.5 litres (a gallon) next time!