ENGINE OIL
The engine oil is the lifeblood of the engine; it must deal with harsh factors in its
environment, including friction, intense heat, and contaminants.
Friction: Hundreds of moving metal parts rub against each other in your
engine, causing friction. Friction produces intense heat and pressure, which
would destroy the engine in a short time. Engine oil provides a lubricating film
between the tight-tolerance moving parts of the engine to decrease friction and
its negative effects.
Intense heat: In water-cooled or air-cooled engines, approximately 60 percent
of the cooling is achieved by water or air; the oil performs the rest of the cooling
function. As the oil circulates rapidly through the engine at 50 to 70 pounds per
square inch of pressure, it carries heat away from the camshaft, rods, pistons,
and valvetrain. The oil then circulates in the lower structure of the engine, where
it is mixed with cooler oil. This oil is cooled by air passing over the crankcase
(also known as the oil pan).
Contaminants: Contaminants can build up in your vehicle’s engine in the
form of soot, ash, acid, and moisture. These substances form sludge, varnish, and
resins that become baked onto engine parts and interfere with performance and
oil flow. A detergent is built into the motor oil in your vehicle’s engine that
disperses the dirt, keeping it suspended in the oil until it’s filtered out (or drained
away when you change the oil).
Besides dealing with harsh environmental conditions to maintain proper
lubrication of the moving parts, the engine oil performs another vital function:
the prevention of a condition called “blowby,” which causes the engine to lose
power. To the naked eye, the piston rings and cylinder walls of the engine appear
perfectly smooth, but they aren’t. Under microscopic examination, a large
number of “hills and valleys” appear. These impressions provide an escape route
for vapor and gases during the compression and power stroke of the engine.
When this occurs, it is called blowby. Engine oil seals these gaps and prevents
this condition so that the engine can run at maximum power.