I think that my vehicle would probably benefit from having it's lubrication system being flushed out at it's next oil change. Checking prices of flushing oil at local suppliers I noticed that they are now also selling a variety of flushing additives (such as STP Engine Flush).
With flushing oil I would normally drain old oil, half fill with flushing oil, run the engine at a fast idle for a 15-20 minutes to circulate it, drain it again, change oil filter and finally fill up with normal oil. With the additive you don't need to drain the oil twice however, you just add it to the old oil in the engine, run it for 15-20 minutes then drain it out with the old oil and change the filter/oil.
Overall the additive option will be more expensive (£4 per flush rather than £2 per flush for my engine) but will take less time (one complete engine drain/fill rather than two). It would also be more environmentally friendly, as there would be less waste oil to dispose of.
So, aside from the cost/time/waste concerns, is the additive solution as effective or even more effective than using traditional flushing oil? Which results in a cleaner engine? I.e. less gunk from the old oil in the new oil.