Piston-to-wall clearances, piston ring end-gaps, and bearing clearances are specifically tailored to match the engine oil's characteristics and intended operating temperature. This story was ...

Engine oil is an absolutely crucial item for any car, regardless if it's diesel or gasoline. There's actually a good explanation why it tends to turn black.

Like a love-hate relationship, a car engine can be dangerous to motor oil depending on its temperature. How hot the engine is can also affect oil during an oil change.

Steve Zoz, Steve Strepek, Marc Wiseman, Cheng Qian, Engine Lubrication System Model for Sump Oil Temperature Prediction, SAE Transactions, Vol. 110, Section 4: JOURNAL OF FUELS AND LUBRICANTS (2001), ...