There are plenty of different schools of thought on the matter, but the truth depends on what type of car you have.
Engineering Explained on MSN

How do engine oil systems work

How Does Engine Oil Protect Your Engine? How Does It Work? How Do Engine Lubrication Systems Work - Sponsored By Pennzoil Engine oil is used for several purposes: to reduce friction in your engine, ...
Winter weather, salt, and de-icers can cause significant damage to your car's undercarriage and body. Learn how to protect ...
The video walks through the full assembly of a four-cylinder engine, breaking down all 94 individual components that make it function. From pistons and crankshafts to timing systems and fuel delivery, ...