I have an '83 300D with 243K on the clock. It had 193K when I first bought it, and it ran cold (barely 80 degrees celsius in the Florida summer). After a new radiator, thermostat, fluid, etc., my temp gauge now reads at around 100 degrees celsius. However, I wanted to see for myself if it was really running at 100, so I brought it to my dad's firehouse and he put an IR or laser heat gun on it in various places where it would be hottest, and the warmest temp we found was 187 degrees farenheit when warmed up (about 86 degrees celsius) - so I know I'm getting readings about 14 degrees celsius wamer than what it is running. If you have access to a IR or laser heat gun, do it - you might be surprised.