I have a 95 Camaro 3.4 and the temp guage has allways gone up and down as i drive it. when i get the car moving up to 60 mph or even slower and start getting some air flow the guage will drop down to 170. The original Dextron fluid has been changed to Prestone 50/50 mix. Could that be the reason for the drastic temp changes while im driving? I just replaced the water pump and themostat (180 deg) and now im not getting any heat. Even if i sit in gear and the guage starts to creep up, the air is cold. I'm stumped!

 

Welcome to the forum.

If it has electric fans you need to check those. Make sure they're turning on at the right temperature.