With the hot weather upon us here in Atlanta, I too am concerned about high engine temps. So I thought I would try out a different kind of anti-freeze and T-stat just to see if I could keep the car running a little cooler than the usual 100c plus that I normally see. My car is a 95 E320 with 150k miles on it.
First, I installed a Wahler brand T-stat in the car and Mercedes coolant mixed 40/60 using distilled water. The temps. fluctuated terribly, constantly going up and down. They would jump anytime I slowed down and almost immediately drop when I was at cruising speed. This gave my aux. fans quite a workout!!!
After not being to happy with the results, I installed a Mercedes brand T-stat using the same Mercedes coolant. This immediately stopped the rapid fluctuating of engine temps. but it still would creep up and give my aux fans a work out if I idled any length of time. My guess is that the Wahler T-stat was slow to react to changing temps and driving conditions whereas the Mercedes T-stat is much better at keeping temps. gradually increasing and decreasing.
So then I tried the Havoline Dex-Cool mixed at the same 40/60 ratio using the Mercedes T-stat. This showed an immediate reduction in engine temps. Just as an example, I went for a ride today and the engine temps. never exceeded 99'C and that included quite a bit of stop and go traffic with the A/C blasting. It is 97'F outside so this was a very impressive improvement over the Mercedes coolant that I was using.
The Dex-Cool says it is Silicate free and Phosphate free so I don't see where it would hurt anything.
Any comments or similiar results out there?????? By the way, I had intended on using a bottle of water wetter but I don't think I'm going to bother now with results like what I've seen.