Oil's purpose in an internal combustion engine is to flow between and fully cushion and separate the many moving parts of the engine. These moving parts experience high temperatures, large forces pressing them together, and high-speed part movements. Today's engines contain parts that are manufactured to close tolerances.

Oil is manufactured to meet requirements that are identified by the grade and API rating on the container.

Oil's tolerances for temperature, shear pressure, and molecular breakdown should encompass the situations encountered in the given engine while running in a given operating range.

If you drive using an oil that has characteristics different from the oil specified by the manufacturer, that oil may or may not satisfy operating requirements that occur in your engine.

You should compare the specifications listed on the oil you used to the specifications listed on the oil recommended by the manufacturer.

Then, consider the driving conditions your engine will experience while using the not-specified oil. Include, ambient temperature and driving speeds.

Finally, evaluate the meaning of the the specifications that do not match on the two types of oil.

It may be that the difference(s) between the two oils are not relevant to the driving conditions your engine will experience before its next oil change. In that case, it may be OK to use the (somewhat) incorrect oil as long as conditions don't change.

Lots of us make this mistake once, learn, and then never do it again!

Ed M., KY