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Odometer
see Speedometer
OEM See
original
equipment manufacturer.
Ohm
The unit of electrical resistance. One volt applied to a resistance
of one ohm will produce a current of one amp. Ohmmeter An instrument
for measuring electrical resistance.
Oil
A substance that lubricates and cools the moving parts of the engine
and reduces the formation of rust and corrosion. It can contain
additives which fights the corrosion of bearings, keeps small
particles in suspension, reduces engine wear, and reduces
oxidization, minimizes carbon, lacquer, and gum formation. Oil comes
in varying viscosity weights suitable for efficient operation in cold
and hot weather and for engines in varying states of wear.
Oil
Filler Cap The
oil filler cap is a plastic or metal cap that covers an opening into
the valve cover. It allows you to add oil when the dipstick indicates
that you need it. Some cars have the crankcase vented through the
filler cap. Oil which is added through the filler passes down through
openings in the head into the oil sump at the bottom of the engine.
Oil
Gauge The Oil Gauge lets you know the pressure in the oil pump;
and is a direct indicator of the condition of your engine. If the oil
gauge gives very low readings, it means that your oil pressure has
dropped. The engine would soon grind to a halt if the oil is not
forced into the nooks and crannies that need to be oiled.
Oil
Pan The pan that is bolted to the bottom of an engine. Oil
returns to this pan after circulating throughout an engine to provide
lubrication, as well as some cooling effects. Most oil pans are open
inside, but high-performance pans can feature trap doors and baffles
to control the oil during aggressive driving and keep it close to the
oil pump pickup. Another product that can help control engine oil is
a windage tray or a crank scraper.
Oil
Pump An engine-driven pump that delivers oil, under
pressure, to the engine's moving parts.
Oil
Ring The lowermost piston ring that scrapes off excess oil
from the cylinder walls and returns it to the oil pan via vents in
the ring and piston.
Operating
Coil see
Limiting Coil
O-Ring
A type of sealing ring made of a special rubber-like material; in
use, the O-ring is compressed into a groove to provide the sealing action.
Original
Equipment Manufacturer A company that makes cars
and/or trucks. Abbreviated OEM.
Overdrive
Generally
speaking, overdrive (O/D) is the highest gear in the transmission.
On most cars the automatic transmission has 3 speeds and overdrive
(fourth speed). Overdrive allows the engine to have less rpm with
higher speed for better fuel efficiency. When you switch it on, you
allow the transmission to shift into overdrive mode after a certain
speed has been reached (usually 30-40 mph depending on the load).
When it's off, you limit transmission shifting to third speed.In
normal driving conditions the overdrive should be always on.You may
need to switch it off if you drive in a mountainous area. [The
automatic transmission automatically shifts from O/D to 3rd gear when
it feels more load. When it feels less load it shifts back to O/D,
but under certain conditions, e.g., driving uphill or towing a
trailer, the transmission cannot decide whether to stay in O/D or
shift into 3rd speed and it starts shifting back and forth. That's
the time when you may switch the O/D off and help the transmission to
decide] .
You
also may need to switch it off when you want to slow down using the
engine braking, for example, if you're driving downhill. For more
details, check your owner's manual.
Overhead
Cam (ohc) Engine An engine with the camshaft(s)
located on top of the cylinder head(s).
Overhead
Valve (ohv) Engine
An engine with the valves located in the cylinder head, but with the
camshaft located in the engine block.
Oxygen
Sensor The oxygen sensor(s) are installed in the exhaust pipe
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of
the vehicle. The sensor measures the oxygen level in the exhaust
gases (how bad the emission is) and gives feedback to the vehicle
computer, which in turn adjusts the air/fuel ratio to keep the
emission low at maximum engine efficiency. If you're having problems
with the emission, the oxygen sensor is one of the first things to blame.
Also
called a Lambda sensor. |
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