Water: Fuel burns to CO2 and H2O.
For every liter of fuel burnt, a liter of water is created.
This normally passes out through the exhaust when the engine is hot, but when cold it can run down and collect in the oil. This leads to sludge formation and rust.
Soot and carbon: These make the oil go black.
They form as the result of incomplete combustion, especially during warm-up with a rich mixture Lead. Tetraethyl lead, which used to be used as an anti-knock agent in petrol, passes into the oil.
A typical used engine oil may have contained up to 2% lead, but today any lead comes from bearing wear and is likely to be in the 2 – 12 ppm range.
Fuel: Unborn gasoline or diesel can pass into the lubricant, again especially during start-up.
Abrasives Road dust: This passes into the engine through the air-cleaner.
Composed of mall particles of silicates. Wear metals. Iron, copper and aluminum released due to normal engine wear.
Chemical products: Oxidation products.
Some of the oil molecules, at elevated temperatures, will oxidize to form complex and corrosive organic acids. Depleted additive remnants
Around 55℃, gasoline start to release form the waste oil.
Around 90-100C, water released from the waste oil.
Around 110℃ – 220℃, diesel released from the batch.
Around 220°C-300°C, Light base oil are distilled out
Around 300℃ -350℃., the heavy base oil distills out