Petroleum is the general term fro crude oil and gas.

Petroleum actually refers to crude oil, which often includes some dissolved natural gas, as it is extracted from the ground. On the commodities exchanges, there are prices quoted for different types (grades) of petroleum, the most popular/common of which is often called "sweet crude oil," referring to its low sulfur levels. "Oil" refers to all different types of oils, including petroleum oil, vegetable oil, and animal oil.

The price of petroleum as quoted in news generally refers to the spot price per barrel (159 liters) of either WTI/light crude as traded on the New York Mercantile Exchange (NYMEX) for delivery at Cushing, Oklahoma, or of Brent as traded on the Intercontinental Exchange (ICE, into which the International Petroleum Exchange has been incorporated) for delivery at Sullom Voe. The price of a barrel of oil is highly dependent on both its grade, determined by factors such as its specific gravity or API and its sulphur content, and its location. Other important benchmarks include Dubai, Tapis, and the OPEC basket. The Energy Information Administration (EIA) uses the imported refiner acquisition cost, the weighted average cost of all oil imported into the US, as its "world oil price". Source: Wikipedia

Thank you, everyone. First I got confused a little bit, but now I think petroleum = 原油、oil = 石油　in Japanese. Thanks again;-)

The oil price is the price of crude oil. i.e. oil that has not been processed Petrol or Gasoline (gas) in the US, is a specific product of crude oil.