First, you don't have to go in any particular direction or even around. Second, if you see a can get right to it, if you manage to pick it up you will probably get your licence. Usually you will not need more then two cans... but time on track is the key and that is extended by picking up the gas. If you miss it, I twill be a 5 minute recharge unless you restart VMK which I found is quicker. Note if you are having problems have a friend go out and sacrifice for you, more cans will come up with others on the track but unless you know them, they will snatch them away.