this is my input after carrying out an engine flush today.
mine is a 190e 1993 car with 114 k miles on the clock.
the problem was of noisy lifters on startup when cold and also intermittently when hot ,so i decided to use engine flushing oil made by morris, a uk firm specialising in lubricants.
i drained the old oil which looked black/dirty-put in 5 litres on engine flush and ran the engine at idle for 10 minutes,then drained the flushing oil.
next i replaced the oil filter with a new one before finally topping the engine with 5 litres of 10w/40 semi-synthetic oil
verdict--wait for it
still get the noisy lifter ticking noise on startup and intermittently when hot-so it did not work for me as it must be a worn out lifter.