Big Oil is a simulation where the player manages a company in the oil business. The first part is played like most tycoon games: the player finds himself on a undeveloped piece of land and constructs all the buildings and infrastructure necessary for a functional oil production. This includes a city for the workers. Then, in theory, the player can lean himself back and watch how the business is developing.
But because the player manages a big company there are many such production sites to care for. And because the whole game is played in real-time - the slowest setting is one day per second - this results in a hectic gameplay where fast decisions have to be made. Especially when a few events happen at the first time, e.g. a new research result or a country sells a new drilling permit.
The game features a free playing mode from 1900 to 2000 (without AI opponents) and 17 historical scenarios, e.g. directly after Pearl Harbor. Additionally the player can choose between two playing modes. In the extended mode the player has to care about everything on every branch, the easy mode focuses more about the overall economic management.