How good or bad is petroleum for the engine

Many of those products are nothing more than kerosene or light oils that will do very little lubricating while in their cleaning cycle while actually allowing some wear metals. If your engine is really dirty, it might cause the clogging of ducts or break-off of carbon particles that can score the engine parts before getting removed in the filter.
Most engines don't really need additional cleaning if a good oil is used. For those that need it, something like AutoRX (I don't sell it, but believe in it) will work over time, gradually cleaning it up. I believe it uses Esters do do the cleaning while still lubricating.
This is one of those things where if it is cheap it is no good. If it is expensive, it might have esters and synthetic components that are good, but price alone does not garantee any result.
Do a search on google to find the experiences with the products you are considering.

tuong,

Many of the mnfrs, suppliers, dealers of "magic oil" are fly-by-night operators. Dont trust them.

Teflon a Dupont patent did not stand up to the test of time, when dosed with fuel or lube. Telfon no doubt has great anti-wear application, but what is the best way to deliver to the moving parts, like in an engine. No answers yet.

Hussam Adeni