changed thermostat thursday on my honda civic aerodeck es 98, now temp running normal while stood idling but when driving drops to cold any advice on this please

 

What's the temperature outside? I've noticed even on the coldest days in florida 40 degrees out this was a normal occurrence even with the engine "warmed up" if it's freezing where you live that could be a factor in why it drops to cold while driving.

 

It is cold here, and my car doesn't do that. Something is wrong if the needle doesn't stay at the normal warmed up reading through various driving conditions. About the only thing that can cause over-cooling is a faulty thermostat that doesn't close all the way. The OP may have gotten a dud new one.

 

Did you have that same problem before the new thermostat?