Here are the rules I’m going to use to my oil refineries:
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Cost: 10
Move: 0
Attack: 0
Defense: 0 (AA ability)
Oil refineries give the nation that possesses it an extra 1 IPC income. These refineries can be built in any land territory you control; you can only have one per territory.
These facilities just like AA guns are destroyed when captured by a nation.
Convoy disruption ability:
The oil Refineries also helps you when your enemy is disrupting one of your convoys. If you have an oil refinery anywhere on the map and your enemy is disrupting one of your convoys with one ship you don’t lose any IPC. You don’t lose IPC’s from convoy disruption has long has you have the same number of oil refineries has your enemy has ships doing convoy disruption. For example Germany has 2 ships in a UK convoy, and UK has an oil refinery in South Africa, in this case UK only loses 1 IPC. This ability only works as long has you have oil refineries.
AA ability:
Oil refineries have AA ability just like any other facility.