Final answer:
The combining form that means oil is petr-. Petroleum is a common source of various oils and fuels.
Step-by-step explanation:
The combining form that means oil is petr-. Petroleum, also known as oil, is a common source of gasoline, diesel, kerosene, lubricating oils, and tar/asphalt. Octanol, represented by the chemical formula C8H17OH, is the standard oil phase used in determining oil-water distribution ratios.