What's the difference between synthetic and conventional oils?

It really all boils down to being refined natural crude oil for conventional and man-made oil from chemical compounds that typically use some crude oil for the base.

SYNTHETIC OIL

• Crude oil base (from the ground)

• Chemical compounds (polyalphaolefins or esters, man-made)

• Additives (Detergents and anti-wear agents, man-made)

CONVENTIONAL OIL

• Crude oil (from the ground)

• Refined, which varies if it will be used to make gasoline, kerosene, lubrication oils, asphalt, etc. (machined by man)

• Depending on how the oil performs in refining, it will continue on or it will need to be refined more with solvent to meet the API requirements (still crude/machined by man)

• Additives (Detergents and anti-wear agents, man-made)

CONVENTIONAL OIL CANNOT BE "0W"

Because conventional oil is mostly made of crude oil, which lacks the ability to achieve the 0W rating. That is why all 0W-20, 0W-30, etc, are synthetic.