Normal Coolant Temperature?
 

On another topic, I was told that 80 degrees was too cold, that I should have a hotter thermostat. I have looked at the Owner's Manual (occasionally I do read the directions!) and it is really useless, mentioning only not to drive in the red zone as the car might catch fire!

Can I please have some more opinions of that other gentleman's post? Too cold? What thermostat should I get?

For the M103? You have 79C or 87C... or 174F and 189F. Sure that's when it opens, but it's too soon for me for the 79C. Remember, vehicles need to be hot for oil to move easier plus boil off water (100/212), keep the fuel from washing down the cylinder walls, better emissions, etc.

Now TOO hot can be bad, but the 189F is what the factory chose for it. Maybe they also did this to keep heat in the cylinder head since aluminum disperses heat fairly quick over iron?

Hell, my Z71 and F150 both were spec'd to 195F factory thermostats. I run a bit cooler (180) to allow for more timing advance without the risk of detonation. These still get to temperature with no issues. I did try a 160F once and was FAR too low. Vehicle stayed in open loop for way too long, increased oil changes, decreased economy, etc.

Even with 110mph blasts down the freeway I haven't crept past 100C in my 300sel. Even 100C is still well within factory spec and not really even that hot. Only decent MB comparison I have is my 560 that runs around 83-5C/181-5F most of the time and is spec'd for the 80C thermostats

Hope it helps.

Thanks, Hit! I am also making huge assumptions that the gauges are accurate - after my afternoon run I will zap her with my infra-red thermometer and see if I am in the real ballpark. Likewise, use the Mighty-Vac on the vacuum.

These factory gauges are fairly accurate.