Oil flush
I have Lc200 year 2008 I have never used oil flush in 280,000 ks as it has been serviced at the correct intervals and using the recommended oil. Approximately 6 months ago I noticed a ticking noise on warmup and remained until reaching the correct engine temperature.
I have done some research and it was suggested that there are filters inside the rocker covers and they are prone to blockage “sludge”, blocking oil from reaching some of the tappets. I believe the front tappets mainly.
This means removing both rocker cover and clean the filters (BIG JOB) expensive job.
After talking to a mechanic (personal friend) he suggested trying oil flush first, this was carried out with great success, the ticking noise was greatly reduced.
For how long, time will tell I guess.