Gee, Peter, this is the second time I disagree with you today. Per JimF's website and SteveB's comments, later engines run a lot hotter. The S420 engine temp hits 100C anytime I'm creeping in traffic with AC. Freaked the heck out of me until I checked the archives. JimF sells resistors to trick the fans into coming on sooner but there's some debate over which models have a separate fan sensor and which models share a sensor between fan and ECU (ergo don't mess with it).

Sixto
95 S420
87 300SDL