A gas odor in engine oil is caused by contamination of the engine oil by gas, usually due to a leaking fuel line or malfunctioning fuel injectors. However, it is normal for a small amount of gas to get into the engine oil during normal engine operation.
Gas in engine oil becomes a cause for concern when the volume of gas exceeds 2.5 percent. This results in a significant reduction in the oil’s viscosity, which affects engine lubrication and causes scoring of the cylinder walls. Getting the car to a mechanic as soon as possible can prevent excessive engine wear. The mechanic drains and changes the oil and finds and fixes the fuel line leak or injector malfunction.