Press 't' during the game to bring up the text prompt, then enter "6WARFOGY" to remove the Fog of War.
After destroying an empty oil tower via the 'K' key (LMB & RMB) send an oil driller quickly to that oil source and build a new tower on it. Now you can take 3-4 tankers of oil to become some more extra credits. That can be twice, before the source is empty.
If you have a group of different units, you should press the 'CTRL' key while selecting their destination in enemy territory to adjust the speed of all units of the group automaticly. This means that no unit will be faster as the slowest of them!
The manual contains some wrong information. Here is what it should say.