500 kms on a full tank of petrol isn't so bad if you do a lot of city driving. I can almost never squeeze less than 0.9l/10km (translates to roughly a 570 km range) out of my 2.0, and track days is almost triple that (2.5l/10km, 160 km range) !
If fuel economy is a concern, you have the wrong car
Revving and speeding is simply too much fun in a 147...