Depending where you live trying to keep heat down from this heat generating monster. I've changed my coolant to a 80/20 mix with water wetter. Both split cooling and main loop. Live data for 4 days each of driving with 50/50 and 80/20 and water wetter huge difference. I was only seeing 11-13 over ambiance on AIT's with a virtually instant temps drop or holding steady after pulls. I do also have the Pierburg CWA100 with 2 to 4 pin harness and stock heat exchanger for now.

The previous owner had a bad scoring issue with his 2014 CLS550 and had a 2016 M157 and MCT trans swapped for for just about the same price at a reputable shop in Scottsdale over the N Scottsdale Mercedes. Back to the data.

The main loop on a cool 52 degrees morning last week live data showed a 195 start before a pull this was at 3 am. Wide open stretch of the 101 merged hit a good digit speed and let off back to the speed limit. That pull spiked my temp to 202. Then gulped a big slug of air though the radiator this dropped the temp to 174.2 in about 6 seconds. The thermostat didn't have time to react it dropped so fast. That kinda freaked me out lol. It took the car a bit of time to close it back off to bring temp back to 195 cruising speed.

What i found out about AMG temp sweep gauge is very accurate to the live data I was capturing. So if your able to take advantage of less molasses thick coolant I'd do it. Even if its the split cooling loop. For the summer heat here in the desert our cars will be much happier.

But water wetter really does work in my instance and it's been close to a month. Ive been checking the expansion tank and split cooler reservoir. Nothing bad or floaties I can see. I am doing this as a long standing evaluation to see if it does degrade or makes worse over time. But so far amazing results!

Love to add nice hood vents to really let it breathe just not sure if its to Mustangy lol for our elegant looking autos.