You can usually find the recommended oil for a car engine on a label under the hood or in the owner's manual. Two-stroke engines, like those found on lawn appliances and some motorcycles, require a special type of oil that mixes with the fuel. Some motorcycles cannot use synthetic oil, because it prevents the clutch from working properly.

Oil comes in different viscosities or grades, and you should really do what you can to find out the required grade, but new oil of the wrong grade is usually better for a motor than oil of the right grade that's 10,000 miles past its service life.

Engine oil.

The recommended oil is usually on the oil cap. Or, check the owner's manual. Or, ask a local dealer that sells the Make of the car.

it depends on the engine. There is no one answer for all.