Terms Starting with O


Octane number-A number used to identify the resistance to burning of gasoline.

Ohm’s law-Voltage equals amperage times resistance (E = I x R).

Oil gallery-The main or center passageway inside an engine block through which oil flows to feed all other components in the engine that need oil.

Oil relief-A small machined area on the side of a lifter that allows oil to circulate around the body of the lifter.

Open circuit-An electrical circuit that has a break or opening in a wire, producing infinite resistance.

Open loop-A computer condition in which the air-fuel ratio is being controlled on the basis of a set of preprogrammed conditions.

O-ring-A type of static seal used to eliminate fluid leakage between two stationary parts.

Oscillation-Fluctuation or variation in motion in an electrical current.  In reference to an automobile, when the vehicle hits a bump in the road, the body oscillates up and down.  Shocks are used to reduce oscillations.

OSHA-Occupational Safety and Health Act of 1970.  This act provides safety regulations and rules for industry.

Overdrive-A gear system used on a transmission to reduce the speed of the input.  Without overdrive, the highest gear ratio in a standard transmission is 1 to 1.  Overdrive systems on a transmission have a higher gear ratio of approximately 0.8 to 1.

Overhead camshaft-An engine camshaft located directly on top of the valves, used on I-head engine designs.

Overrunning clutch drive-A type of drive on a starter motor that uses a series of rollers that lock up to cause the pinion gear to rotate.

Oxidation-The process of combining oil molecules with oxygen.

Oxidation inhibitors-Additives to fuels and lubricants that reduce their reaction with oxygen.

Oxides-Chemicals that form when certain pollutants combine with oxygen.

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