There's two points of view on this one and, to be honest, I don't know which one is which. This is in regards to the frequency of cleaning. Some say NOT to clean it out because it may cause compression issues and leaks.

Then, there's the exact opposite where, some say by removing all the nasty stuff, the engine works better.

But, the thing is that we have two scenarios and they are:

-low mileage engine / low wear

-high mileage / high wear

Folks claim it ruins / causes more issues cleaning a high mileage engine than not. And, conversely, you'd want to keep the new engine clean as possible to prevent blockages, sticking parts etc.

Now, as far as eating gaskets; it is possible and, I have heard of this many times. Putting oil in there is one thing but, to put fuel inside the engine (especially diesel) is another. The seals are there to seal against motor oil leaks and were designed to be chemically impervious to oil. But, when you take fuels and start to run that inside the engine, now it's really unknown as to what affect it will have on the seals. The other thing is, depending on what the seals are made out of is of importance because, if you have an older vehicle that has rubber gaskets and silicone, it's not going to be compatible as diesel fuel has a severe chemical affect.

In light of looking into using diesel fuel to clean an engine, I personally would not use it.

 

as a flush thread, this could go on and on forever.
i'll say this and then shut up.

you should only flush the engine when you know you have sludge built up and can see it in the valve covers or oil pan, etc. i wouldn't overdo it. with modern oils, maybe once every 100k miles.

diesel fuel can be mixed into the oil as a flush. don't drive it, just idle it for awhile. my gut feel is that it doesn't hurt anything.

another homebrew is to replace one or two quarts of ATF. its 10w oil and loaded with detergents. i don't think it hurts gaskets or seals at all.

another option is to buy an engineered engine flush, like Gunk brand or other. it looks and smells like it has a lot of solvents, but i don't think a rare treatment will hurt anything. i feel confident that its passed reasonable tests by the maker. if it didn't, they'd be eat up in product liability problems.

the hard part is knowing that you made any difference. you'd have to pull a valve cover or pan or something both before and after to really know.