[Uncle Bob]

Here we go again.

DO NOT use hypoid gear lube in a crankcase just because the viscosity may be of a similar grade to what you want to use. The extreme pressure additive contains sulfur/phosphorus which will dine on your main and rod bearings.

It is true that piston type compressor oils typically don't contain detergents, and can be had in correct viscosity grades for a motor vehicle, however they are often made from naphthenic base stocks that are less thermally stable than the parafinic base stocks that every non-synthetic crankcase oil is made from.

Crankcase oil detergent/dispersants don't act like an often advertised bathroom cleaner.......they are not "scrubbing bubbles". Their primary action is to suspend contaminants (mostly by-products of combustion as correctly noted by deuce roadster). Most dislodging of built up deposits comes from fluid movement.

Putting a "quart" of MMO in an engine would probably cause much more "detergent" like action than regular motor oil since it contains a solvent.