Hi All, I have a SBC 350 motor in a 53 Chevy. The fan is a mechanical one on the pulley. I know I should eventually look into an electric fan, a shroud, etc. Prior to moving to an apartment with a tiny garage, I had a 2 car garage and I did a lot of work to the car. I drained the coolant and put 50 percent Prestone concentrate and 50 percent water. I'm not sure if that made it worse but my motor is running rather hot. The ambient temps were 74 degrees today in San Diego. At stop and go roads, the motor runs around 200 degrees, and at a stop light it gets close to 210 and even close to 220 at times. Going a little faster on the road it drops a little below 200. Prior to changing the coolant it might have run 5 to 10 deg cooler in each of those scenarios. The previous owner said it might have a 195 deg thermostat. What should I do in the meantime (putting an electric fan and shroud is a project I will have to wait a few months to do)? He said there is something I can add to the coolant that works like a miracle to provide coolant but I forget the name of it. I wonder if he had put that in the coolant before.