Fuel Mileage..whats the usual and how can you improve it?

[twitchy]

I have a 93 240SX SE which is basically stock, the only modifications are the removal of the factory intake baffle as well as a slightly larger exhaust pipe (although it has a cat and goes into the stock muffler)

My question is this:
What should my car get for fuel mileage (IE Range. Its a 50 liter tank, so how many kms?) and

How can I improve it


Considerations:

-I change oil regularly (5000 kms, semisynthetic)

-Gearbox and Diff fluid just changed last month

-I drive the car enthusiastically, but usually shift at 4000 rpms or so, once in a while give it some stink, rarely sees redline

-I think it would be the same on most cars, but the fuel gauge drops more slowly in the middle 2 quarters than the top or bottom quarter

-Slight slop in front end, maybe it needs an alignment, or something, nothing major though.

-Drove with all my friends from Sudbury to Brit and back. The trip consisted of roughly equal parts highway and city driving. Comparing all the cars to one another, I had the worst mileage of the 4 on that trip.

2002 Mustang GT: V8 4.6 liter. Used quarter tank
2002 Mustang GT: 4.6 liter, open exhaust. Used quarter tank
97 Tiburon FX: 2 liter I4. Used quarter tank
87 Mustang 5 liter. Used quarter tank.
My 93 240SX used a little over half a tank on the same trip!! (all cars manual with 50 liter tanks)


Has anyone tried mileage-boosting products? Could I need a new O2 or MAF sensor? ANy ideas as to why my car burns more gas than an engine twice its size would be appreciated!

Thanks