For many reasons and whatever reasons, many car owner want to clean the internal engine, flushing out residual oil along with decade-old deposit. Many techniques, tools and chemicals are used to get rid of the dirt in your engine.
After some research and googling, I conclude that...
1. Chemical flushing is very dangerous to your engine. Not all engine and material in the engine are universal, some chemicals may harm your engine parts, i.e the gaskets, rubber parts, seals. Remember that the materials that made up your engine parts vary and might react to the chemical cleaner as most are meant to INTENSIVELY flushing out carbon. Ironicly, some materials in engine are made of carbon (your fuel line etc) ... might be harmful and be corroded.
2. Alternative to that, some use double draining technique by draining the engine twice. At the second drain, to use cheap engine oil/ oil filter for the in between period. I would say is OKAY but make sure it comes from reputable sources. You don't want your car engine oil turns 'puding', the cheap engine oil might not be engine oil after all - fake/recycled.
3. Recommendation.... (not liable on me, just a suggestion) use engine oil for diesel engine for cleaning. Why? The engine oil for diesel engine has more additive (detergent) coz diesel engine makes more deposit. Drain this oil after running your engine for awhile, some claim for several to ten of kilometers. I EMPHASISE is ENGINE OIL FOR DIESEL ENGINE not DIESEL!