This is most useful when used with factions who are already hostile (to keep them from shooting you down), but can also be used to keep friendly factions from becoming upset with you. Get one of the helicopters used by the faction you want to steal from (or one of its allies), and allow your disguise to finish. Fly to the location of the fuel you want to get, and lower your winch. Grab the fuel tank, and lift off before the enemy soldiers recognize you, then fly to a secure location (either the PMC or a remote, open location). Once out of sight, call Ewan in for the pick-up. Note: Using a heavier helicopter is recommended, as the Rogue and Gunney class choppers are extremely difficult to control when carrying a heavy fuel tank. Also, there are at least half a dozen fuel tanks relatively close to the PMC, most of which are controlled by Universal Petroleum. Spending the fuel for an Ambassador Gunship (an Allied helicopter, who are allies with UP) is well worth it if you are going to use your PMC as a fuel depot.
Use the following trick to steal fuel from a friendly faction without having to worry about affecting their status towards you. Go to an outpost that has fuel tanks, and tag them. Then, call in Ewan for the extraction. If a soldier happens to call in a report about your hostile act, go inside the outpost to cancel the call. By doing this you will get fuel and the faction will still be friendly with you.
This trick requires a fast vehicle (for example, a sports motorcycle). Find an outpost that has a fuel tank. Look for an easy way out before you attempt to steal the fuel. Once your vehicle is positioned facing the fast exit, and after making sure no one sees you, tag the fuel tank, and call Ewan for extraction. Run to your vehicle, and drive as fast as you can until you are far enough from the place so that no one can report you. Note: This also works with a helicopter as your vehicle when you are in the jungle area, but requires more time because you must wait a few seconds before you can lift off.
Fly a chopper with a winch. Winch a car and throw it on top of other cars to destroy them.