600 SL 93 thermostat
 

Standard thermostat is 87C. Are there any lower reading models eg. 82-85C available?. Also where are the coolant drainage points and any bleed screws?. What is the best flushing materials. Mechanic states citric needed only when oil in system. Prestone anyone?.

You do not want to go lower on the thermostat, this will create unnecessary problems if the engine runs too cold consistently. Citric acid flush is very effective, I have never tried the prestone flush, and I probably wouldn't want to use it. Drain plugs are on the block (Sorry I do not know where on the block on the 12 cylinder) and at the bottom of the radiator.