Australian Automotive Glossary

Oil Filter

A cartridge-filled canister placed in an engines lubricating system to strain dirt and abrasive materials out of the oil....
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On-board Diagnosis System

A computer-controlled system that identifies malfunctioning or out-of-adjustment components under its control through the display of fault codes. The presence of fault codes is usually indicated by an intermittently or constantly lit "check engine " or "service engine soon" light....
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Outdoor Power Equipment (OPE)

Relates to a wide variety of light and heavy outdoor machinery including lawnmowers, chainsaws, pumps and generators. Technicians in this field can find themselves working on specialised equipment and with high tolerance testing and measurement equipment....
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Overdrive

A transmission in which the highest gear ratio is less than a one-to-one ratio. This means the drive shaft turns faster than the engine crankshaft. The overdrive feature saves fuel and, because the engine runs slower, engine wear and noise are reduced....
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Overhead Cam (OHC)

The type of valve train arrangement in which the engine's camshaft is mounted above the cylinder head(s). When the camshaft is placed close to the valves, the valve train components can be stiffer and lighter, allowing the valves to open and close more rapidly and the engine to run at a higher RPM. In a single overhead cam (SOHC) layout, one camshaft actuates all of the valves in a cylinder head. In a dual overhead camshaft (DOHC) layout, one camshaft actuates the intake valves, and one camshaft operates the exhaust valves....
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Overhead Valve (OHV)

An engine with both intake and exhaust valves placed directly over the piston. In this design, the camshaft is located in the block, and the valves are actuated by pushrods and rocker arms....
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Oversteer

A handling characteristic of a vehicle that causes it to turn more sharply than the driver intends because the rear wheels are sliding to the outside of the turn....
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