Liquid that reduces friction or wear, or both, between the moving parts within an engine; removes heat, particularly from the underside of pistons; and serves as a combustion gas sealant for the piston rings.
- Thicker oil reduces surface contact of load-bearing surfaces.
- If the oil is much thicker than required, friction and losses will increase.
- Thicker oil increases losses through internal fluid friction and churning losses.
Engine oil may contain additives to enhance certain properties. Inhibition of engine rusting, deposit formation, valve train wear, oil oxidation and foaming are examples.
A lubrication system in which the oil is pumped into the engine’s sump under pressure and then pumped out again. This reduces the losses from the oil being churned around by the crank and big ends at the same time as allowing it to be cooled efficiently.
Other benefits are:
- Allows the crankcase to be reduced in size
- The engine can be installed lower in the chassis
- Eliminates oil starvation when the car is subjected to acceleration, braking, and cornering forces generated by a racing car.
Most oil we buy is classified: xxW-yy e.g. 10W-40
- The “W” stands for winter
- 10W part is the winter rating, the lower the number the lower the viscosity at low temperatures
- 40 is the viscosity limit at 100°C
- The lower the number the thinner the oil
The amount of lubricating oil an engine uses. In 2-stroke glow engines the oil is part of the fuel and all of this goes through the engine and combustion chamber.
Oil Control Rings
The piston ring, usually located at the lower part of the piston, that prevents an excessive amount of lubricating oil from being drawn up into the combustion space during the suction stroke.
It is quite unusual to have oil control rings on a model engine – normally we’re all quite happy to burn a small amount of oil. Also, the engines don’t run that long and so the amount of wear is minimal.
Designed to chemically neutralize acidic contaminants in the oil before they become insoluble and fall out of the oil, forming a sludge.
- These oils are mainly used in combustion engines.
A channel or channels in a bearing to improve oil flow through the bearing.
Oil Mist Lubrication
A method of lubricant delivery in which oil is piped throughout the machine to desired locations and dispensed with a spray nozzle.
Device used to prevent oil leakage past a certain area.
Oil Splash System
Engine lubrication system where the end of the connecting rod dips into the oil in the sump and splashes it around the crankcase.
An unstable free vibration whereby a fluid-film bearing has insufficient unit loading. Under this condition, the shaft centerline dynamic motion is usually circular in the direction of rotation. Oil whirl occurs at the oil flow velocity within the bearing, usually 40 to 49% of shaft speed. Oil whip occurs when the whirl frequency coincide with (and becomes locked to) a shaft resonant frequency. Oil whirl and whip can occur in any case where fluid is between two cylindrical surfaces.
The reaction of the oil with an electron acceptor, generally oxygen, that can produce deleterious acidic or resinous materials often manifested as sludge formation, varnish formation, viscosity increase, or corrosion, or combination thereof.
Distress marks on sliding metallic surfaces in the form of long, distinct scratches in the direction of motion.
Abnormal wear due to localized welding and fracture. It can be prevented through the use of antiwear, extreme-pressure and friction modifier additives.
Ability of lubricating oil to withstand physical change under severe operating conditions.
Water displaces most oils, with the exception of animal based oils, and so special compounded oils that lubricate in the presence of water are needed for steam engines. Modern steam oils contain 4% tallow oil by volume – this allows the oil to work in the hostile internal environment of the steam engine.
Oil producers add several compounds to steam oil to help stabilise viscosity and lubricity; hence the name compounded steam oil.
An engine lubrication system where the oil sits in the sump under the crank, is pumped around the engine and drains back to the sump.