The American Petroleum Institute (API) is the largest U.S trade association for the oil and natural gas industry. It claims to represent about 400 corporations involved in production, refinement, distribution, and many other aspects of the petroleum industry.

The association’s chief functions on behalf of the industry include advocacy, negotiation and lobbying with governmental, legal, and regulatory agencies; research into economic, toxicological, and environmental effects; establishment and certification of industry standards; and education outreach. API both funds and conducts research related to many aspects of the petroleum industry.

API Standards Committees are made up of subcommittees and task groups that works and maintain these standards. the list of Committee and Subcommittee is:

Committee on Standardization of Oilfield Equipment & Materials (CSOEM)

SC2- Subcommittee on Offshore Structures

SC5- Subcommittee on Tubular Goods

SC6- Subcommittee on Valves & Wellhead Equipment

SC8- Subcommittee on Drilling Structures & Equipment

SC10- Subcommittee on Well Cements

SC11- Subcommittee on Field Operating Equipment

SC13- Subcommittee on Drill Completion & Fracturing Fluids

SC15- Subcommittee on Fiberglass & Plastic Tubulars

SC16- Subcommittee on Drilling Well Control Equipment

SC17- Subcommittee on Subsea Production Equipment

SC18- Subcommittee on Quality

SC19- Subcommittee on Completion Equipment

SC20- Subcommittee on Supply Chain Management

Committee on Refinery Equipment (CRE)

Subcommittee on Corrosion & Materials

Subcommittee on Electrical Equipment

Subcommittee on Heat Transfer Equipment

Subcommittee on Inspection

Subcommittee on Instruments & Control Systems

Subcommittee on Mechanical Equipment

Subcommittee on Piping & Valves

Subcommittee on Pressure-Relieving Systems

Subcommittee on Aboveground Storage Tanks

Pipeline Standards Committees

Safety and Fire Protection Committee (SFPS)

API Committee on Petroleum Measurement (COPM)

Committee on Evaporation Loss Estimation

Committee on Gas Fluids Measurement

Committee on Liquid Measurement

Committee on Measurement Accountability

Committee on Measurement Quality

Committee on Production Measurement & Allocation

Committee on Measurement Education & Training

API also defines the industry standard for the energy conservation of motor oil. API SN is the latest specification to which motor oils intended for spark-ignited engines should adhere since 2010. It supersedes API SM.

API also defines and drafts standards for measurement for manufactured products such as:

Precision thread gauges

Plain plug and ring gauges

Thread measuring systems

Metrology and industrial supplies

Measuring instruments

Custom gauges

Precision machining and grinding

ISO 17025 registered calibration

API RP 500 and RP 505 classify the locations for electrical equipment in hazardous areas.

API has entered petroleum industry nomenclature in a number of areas:

API gravity, a measure of the density of petroleum.

API number, a unique identifier applied to each petroleum exploration or production well drilled in the United States.

API unit, a standard measure of natural gamma radiation measured in a borehole.