How does drinking more fuel equate to more mileage ?
Lets say for a stockish condition car, it can go up to 260kms fuel consumption is around 12kms/litre
mildly modified, it goes up to 200kms on hard driving conditions for fuel consumptions up to 9kms/litre
At the end of the day, u only travel less with a more modified car and of course varying driving styles.
Be it stock or modified, it doesnt really affect the mileage. It drinks more fuel yes, but also, it travels less distance.
For a 2001 ish car , you should be looking at 50k kms mileage. Again that is a rough figure but it should not sway too much from there.