Thanks for contacting WorldWarfare Support.
Oil collection can depend on which type of battlefield you are in. If you are Isles of War, for example, and you are at the outer ring, then the oil output can be poor. Keep in mind that some oil field outputs are not that great.
If you feel that your oil output is incorrect, do let us know more details about this and what type of battlefield you are in, along with the zone and battlefield ID and we will investigate!