Something I was wondering about. Is there any advantage (or disadvantage) to running one of the warm weather (grey colored) thermostats?

I don't have any problems with overheating, even in traffic during the summer with the AC going, but I was thinking it might be better for the engine to run at a lower temperature.

 

look two posts above yours

 

There is a big advantage to lowering your engine operating temp. The Motorad 439-180 sells for $40 on Amazon and does a great job especially if used with green coolant, like Peak and a bottle of Water Wetter.

 

Considering that older Rover engines, like the 3.9 liter V-8 in a 94 Defender, used a 82 degree C stat, and that was fully open at 82 C, lower temp makes sense to me. Here's page 153 from the Defender manual. Now we don't have a lot of Defender's on here; not too common in USA. But does not seem like you get as many complaints about overheating, etc. If 180 or a little less was OK in 1994, jumping up to 195 - 220 (which may people find out they are running) seems like it could make plenty of things not behave under the hood.

 

The engine is more fuel efficient and emits fewer pollutants when it runs hotter, but as noted above a cooler thermostat might help ease stress on components.