[JFP in PA]

Originally Posted by Topless

It is not an issue in Cucamonga. Although when we spend the weekend in Big Bear (1 hr away) at 7500' elevation and there is 6 ft of snow on the ground with temps in the teens my wife might argue that there is no such thing as "plenty of heat" in the cabin.

While you and I may agree that you get plenty of heat with a 160F T-stat and it is probably better for the motor in the long run I am sure all those fine German engineers had a plan when they collectively installed 180-200F T-stats into most modern German cars. My father was an engineer and he didn't tie his shoes in the morning without a plan. Better heater performance is just one plausible explanation. There are many others. Until someone pipes up who was actually in the room when these decisions were made we may never know for sure what they were thinking.

Going way back in this thread; using higher temp thermostats has always been a cheap way to ring a little more emission compliance out of water cooled engines. Literally every car manufacturer out there, European, US and Japanese has used this as a low cost route to compliance. But, as previously noted, it tends to kill volumetric efficiency. Lowering the coolant temp improves the volumetric efficiency and the band width of the DME allows the A/F ratio to correct and still use more timing (with in the DME algorithm limits). Running the engine hotter is not better for the engine, it is worse; but because the OEM has to warranty the emissions system to work for 80,000 miles (Federal mandate), they set it up to make it easier to pass when the engine had a lot of miles on it. But, because the engine warranty lapsed much sooner, if the engine fails, it is not the OEM's problem, it is yours................ So the bean counters over rule the engineers, you get a less efficient engine with a potential for premature breakage. And where the bean counters have less sway, say with the GT2 or the RSR cars, and max performance is the target, you find 160F thermostats as factory parts……..