Aviation engine oil serves several important functions: 1) It absorbs heat from moving engine parts to cool bearings and piston rings. More so than in automotive engines, oil carries off a greater percentage of an aviation engine's heat. 2) It seals between rings and cylinder walls and helps retain seals around gasket areas and crankshaft seals by washing around these areas. 3) It cushions engine components through various lubrication forms including boundary, mixed, dynamic, hydrodynamic, and elasto-hydrodynamic lubrication.

2. Absorb heat

3. Seals

4. Cushions

5. Cleans

6. CorrosionAbsorbs Heat -Oil is a heat transfer medium which flows through the crankcase and oil coolers, and dissipates the heat from moving parts, thus constantly cooling engine bearings and piston rings. -Air-cooled aircraft engines rely on their oil for cooling far more than water-cooled automotive engines. Automotive oil typically accounts for about 40 percent of the engine's cooling capacity. In aviation engines, the oil must carry off a greater percentage of the engine's heat. Seals -Aviation oil not only provides a seal between the rings and cylinder walls, but also helps seal the gasket areas and the rubber or synthetic seals for the crankshaft. When oil washes around those areas, it helps retain a seal. Thus, aviation oil must be of a blend or formulation that is compatible with the seal materials so that the seal itself lasts longer. Cushions -Oil properties can include boundary or mixed film, dynamic, hydrodynamic, and elasto-hydrodynamic forms. -Boundary or mixed film lubrication is found in the upper cylinder area in the outer boundary of an aircraft engine. This is the most remote engine area to lubricate because the oil rings scrape most of the oil film off the cylinder walls before it reaches the upper cylinder. However, there must be a residual amount of lubrication in the upper cylinder to protect the engine on startup. Also, if an engine has been sitting idle for a month, some lifters have been pressed against cam faces and loaded under maximum spring pressure. Most of the oil has been squeezed out of that junction. Cleans -All aviation oils clean. When we say aviation oil cleans, we think of removing sludge, varnishes, and grunge accumulations in the oil pan, on plugs, or in the screen. However, when a lubricant keeps your airplane engine clean, it also means a clean ring belt area and better control of the combustion process. When those rings are able to move freely, your engine operates at higher efficiencies, has better ring seal, produces less blow-by, and consumes less oil Corrosion -Ash cannot be added to aviation piston engine oils. Regulations prohibit the use of ash-bearing detergents and anti-wear, zinc-dithio-phosphate that are used in automotive or diesel truck engine oils because they may cause pre-ignition or detonation in an aircraft engine. -Dispersants, flow-improvers, anti-foam, anti-rust, anti-corrosion, and oxidation inhibitors can all be found in aviation oils, as can some ash-less, anti-wear additives.