Where is the coolant temp gauge needle supposed to be for normal operating temp? Mine points to about a quarter of the way up on cooler days and almost half way on hotter days. That difference also doesn't seem normal, shouldn't the coolant system keep the engine at a constant temperature regardless of ambient temperature? I replaced the thermostat within the past year.

Did you use the subaru thermostat?

I'm not an expert but have read on here that aftermarket thermostats have smaller openings. My loyale runs about quarter way up on the gauge I think that's normal.

I find it normal to run below the half mark. Generally at about the 1/3rd mark. 

 

It should not vary between warmer and cooler days unless there are issues with the cooling system. OEM thermostat means a lot with these cars. 

 

Don't sweat it unless your temperature goes above half, or fluctuates a lot. Make sure coolant is full and air is burped out.

 

Look for any signs of coolant around the timing belts as the water pump will leak from the weep hole once it wears past its service life. 

 

An old water pump may become inefficient. Old radiators become corroded.

 

Frequent coolant changes (30,000 mi or 5 yrs) help prevent cooling system corrosion.

Hmm, looks like I might just need an OEM thermostat. I used an aftermarket one. I don't see any leaks and I haven't really broken into the cooling system except for the thermostat, so I don't know if it's burped or not. Coolant level is fine.

Finally got around to installing the OEM thermostat and my needle is now pointing around halfway. Thanks!