This post is also available in: 日本語 (Japanese)
ENGINE OIL FACTS
Lubricate engine parts
Inside your engine, pistons, crankshafts, camshafts, and other parts are rotating at incredibly high speeds – sometimes at several hundred or several thousand revolutions per minute. Engine oil lubricates these metal parts to keep wear and burnout to a minimum.
Create tight seals
Pistons do not fit tightly into the cylinders in your engine. Instead, they are surrounded by a tiny gap that allows them to move freely. If this space is not sealed tightly, the energy produced from combustion can escape from this gap, resulting in power loss and blow-by gas emissions. In older engines, this gap often gets wider due to repeated wear from the piston rotations inside the cylinder. If this happens, a tight seal can be recreated by overhauling the engine and frequently replacing engine oil with new, high-viscosity lubricant.
Cool hot engine parts
The combustion and friction inside your engine creates extremely high temperatures. Engine oil also works as a coolant that absorbs heat as it circulates among the engine parts, then returns to the oil pan to cool. Engines designed for high-speed driving (such as in sports cars and race cars) generate even higher temperatures, and are often equipped with a separate oil cooler.
Clean the engine
Engines produce a variety of contaminants as a result of combustion and rotational motion, which are often called sludge. Sludge build-up will not only affect engine performance, but will also shorten engine life. Engine oil plays an important part in absorbing and/or dispersing these contaminants to prevent accumulation. Black engine oil is usually a sign that the oil is doing its job and cleaning the engine, but there is a limit to how much sludge oil can absorb. That is why oil must be changed on a regular basis.
Combustion produces scorching temperatures inside your engine, which are much higher than the surrounding air. This creates a temperature gap that often causes condensation, which in turn encourages rust formation. Rust can both deteriorate engine performance and shorten engine life. Engine oil helps prevent rust and extend the life of your engine.