My 86 gl-10 turbo has a hard time getting up to temp. When it does it only stays there for a short time. What I mean by this is I have a digital gauge and the temp reading will just go to the warm mark before it will drop totally off. The heat will not blow out hot air, bearly warm. The car runs great but seems to never run at temp always cool. It seems as though it is the thermostat but when I drive it when it is wam outside the car will run at temp andthe heater blow out somewhat hot air. What do you guys think. Coolant is full btw. thanks

My best guess would be a thermostat opening too early. They are rated by degrees in temperature. Try an OEM Subaru replacement from the stealership. Best quality and proper degree rating