Ask one of the lecturers if you can use his or hers and then run a few times to empty the tank.
First empty it in First Gear.
Then Second...
Then Third...
etc...
If you keep a check on how much it costs to fill up the tank, and the price of fuel then with little bit of math you can calculate it.
Go for an RPM check for the speeds you'd in theory expect for each gear, find out what the volume of fuel injected into the cylinders is at each shot and do some more maths.
Compare that theory with your findings and then see if theory fits to practise.
Best I can do at short notice and with minimal information, sorry.