What should I do about fuel when I return the car?

Your car comes with a full tank, so stop at a nearby gas station and fill it up before you return it. If the tank wasn't full at pickup, refill it to the level it was at when you picked it up.

Keep the gas station receipt and show it when you settle up. If you can't refuel or the tank is short, the fuel will be charged at the rental company's standard rates. Filling up yourself is usually cheaper, since you pay only for the gas you actually buy.

Pumping gas in Guam for the first time? There's a step-by-step guide to self-service fueling.