Dear threx666:

The bearings and seals in your engine were made to operate with a specific type of oil which has specific properties or characteristics.

An internal combustion engine uses "SLIDING BEARINGS" vs "Anti-friction" bearings (like ball, roller, tapered roller, needle, etc.) that you would see in your wheels and axles.

They look like hemispherical shells and are used in the MAIN or crankshaft bearings and in the connecting rod bearings.

The critical parameter for this type of bearing to work properly is the lubricant's (engine oil's) Viscosity - its thickness (laput).

In a correctly operating sliding bearing there is NO metal-to-metal contact - everything is supported by a thin film of oil that separates the bearing and the rotating member it carries - called the JOURNAL (hence another name for them is Journal bearings).

This phenomenon is called Hydrodynamic Lubrication.

What is important to remember is that the oil must be thick enough to support Hydrodynamic Lubrication, or else, metal-to-metal contact occurs.

The Engine Oil's thickness is indicated by the SAE number on the container. The oil conforms to a certain viscosity according to the Society of Automotive Engineers. Examples are SAE 30, SAE 40, SAE 15W-40, etc.

If the oil is too thin (malabnaw) the bearing cannot support the journal and so the parts make contact and wear occurs.

Now in order to "flush" the engine, a flushing oil must be thin, therefore, if you run the engine with it inside instead of the correct type of oil, you are courting disaster or at the very least getting premature wear on your engine.

If you want to clean the engine out I recommend you just use a cheap diesel engine oil like Shell's Rotella SAE 30 and pour in the same amount as your engine needs.

Why use a diesel engine oil? Well aside from being cheap, it has strong detergents which will help clean your engine.

Run it for 10 to 15 mins, drain the oil and that should remove the bulk of the dirt in your engine without putting anything at risk.

Regards,

Dusky Lim