I have been keeping an eye on my coolant temps ever since I started Auto-Rx, my coolant sensor probe mounts in the front driver's side cylinder head, and whether I used a 180 or 195 thermostat, the temperature as measured by the infrared gun would always read about 205 degrees, the same temperature was recorded on the passenger side cylinder head in the front. In the back on the driver's side and passenger side I always got a reading of 230 to 235 degrees as measured by the infrared gun. I have a high flow Edelbrock water pump on the car so it is not like I have a cheap water pump. When I aimed the infrared gun tonite at the front heads on both sides it was 205 degrees, when I aimed the gun at both heads towards the rear of the block it was 205 DEGREES, of course I did it again to make sure. What was also interesting was that before my oil temp at the middle of the oil pan was at about 200 degrees and tonite it was 185 degrees, I know this temp is correct because my oil filter temp was about 187 degrees. Every time I have taken a reading at the oil pan the oil filter temp was about the same. This is my thinking, Auto-Rx loosened the crud in the back of the block and now that I am 1800 miles into the rinse phase it is slowly or it already has taken the junk to the oil filter. I cannot think of any other explanation in this matter. I mean if metal is not getting lubricated it is going to be hotter than metal that is being lubricated. My coolant gauge is not fluctuating anymore, it comes up to temp and stays there, no more coming up to temp and then maybe going a little higher and then coming back down a little bit. I am at 362,000 miles and I started Auto-Rx at 343,000 miles, so I have been doing Auto-Rx for 19,000 miles so it must be finally releasing 343,000 miles worth of junk. I think why the temp gauge was jumping around a little was because it was hotter in the back of the block. I will keep everyone posted.