The dealership I work at:
Not given a loaner if any work is under 1-1.5hrs [1.) Unless VIP 2.) If you bitch].
1/4 tank is minimum gas level we can give the car to you at [sometimes we do get desperate though].
You can be charged if not returned at the gas level at which the loaner was given to you 1.) If you pay with credit card the amount can be charged to you afterwards when we see the level - you agree to this when you sign the paper 2.) Most dealerships don't enforce this, but they may start.
We know the loaners are beat on 95% of the time, we aren't stupid.
You have to remember we have 70 people stop by in a day, and have around 20 loaner cars 1.) Not taking into consideration the cars that are overlapped, ie: not brought back when they are supposed to be.
Also remember alot of Infinti Dealerships now have a reservationist, or 1-800 number you call to make appointments, these people aren't always correct on the information they give out. Mishaps happen.

$5 isn't that bad, because like alot of other car dealerships - they don't HAVE to offer loaners! Its just a luxury thing, and something great. You should respect it, but if taken advantage of, like many other things, it can be taken away - a dozen people can ruin it for the hundreds of others at a dealership!