In case if you have a March which does low mpl do the following to get the maximum:
- On time oil change with oil filter change on ever other service (use the genuine filter)
- Check the air filter, if it is hard, dirty or less oily then replace it. If it is in good shape, get it cleaned
- pump 95 octain if possible
- Watch out your drving habits. Rabbit jumps in the traffic blocks, and usless high revving burns more fuel
Having said all these even A*W agrees that toyota is more efficient on fuel. I've heard that Swift is good too, but don't have any experience though