Since your not flushing the whole system it's going to be a bit of a PITA to change the mix in your entire system.What is the suggested annual mix? I'm in Texas- anyone use/suggest any additives?
What range is considered "out of the sweet spot" as in the car being too cool that its not running fully optimal? Of course I got this to have the car run a little cooler but don't want to make it cool out of optimization.After my t-stat install, I refilled with the coolant mix. the car was constantly running in the 193-208* range around the city and hwy. Head temps usually hovered 10-15* over that.
This is where the threads about the high fans on in the Lund tune came in to play. Mine were on ALL the time. The I decided being in Texas and this being a garage queen to drain and refill with distilled water. So I measured pulling coolant mix out of the reservoir (had to do this several times with a syringe and figured could better control it this way) until I reached the estimated 75/25 ratio. Now the temps hover from 178-192* (on long idles) with cylinder head temps not getting over 200* unless again on the long idles but no more than 204*. It's been great as the fans don't kick in unless it's needed and not running all the time on high. This is with some of the recent weather in which has been high 90s-100s.