If all you do are 2-mile runs then the engine will always be running on enriched mixture and your fuel economy will be poor. If you want to find out what it will really do, fill the tank, take it on a 200-mile run, then fill the tank again and do the sums on the basis of fuel used. Another reader complained of the same thing and was taken out by a Hyundai mechanic who averaged 58mpg over an hour in the same car.