Car doesn't seem to warm up correctly...takes forever it seems to get warm? Coolant replacement time or thermostat is shot?

 

Sounds to me like your thermostat is stuck open.The way you can check it without taking anything apart is start the car when it is totally cold.With the engine running,keep feeling the radiator.If it stays cold for a few minutes,then suddenly gets hot,the thermostat is working.But if the radiator gets warmer and warmer ever so slowly,it is heating up with the engine andyour thermostat isstuck open(or missing.......some people take them out thinking it will cool better in the summer)