My 93 dx has normal temp for the most part, but after about 15 minutes of doing 70+ on the highway, the needle on the temp gauge climbs 2/3 to 3/4...as soon as i slow down to 60 or so the temp drops to normal, or as soon as i get on the off ramp the temp gauge drops to normal. Its about 5 degrees in michigan right now, could that be part of the issue?

 

anything blocking your radiator?
have you checked coolant level?

 

thermostat

 

Are you losing coolant?

I think the thermostat may be malfunctioning by closing when the engine is hot. Try replacing it.

 

good coolant level, thermo replaced a month ago with an off brand. guess i shld head to the dealership and get an oem?

 

Well, as instrument mentioned, the cooling system or radiator may be clogged or, alternatively, the water pump may be failing. You might want to flush and bleed the system.

 

oh yeah i dont know if this is related buy my heat is coming out barely even warm

 

This happened to me yesterday in my Del Sol. These are the things I did.
Checked coolant level.
Use a coolant tester to check the MIN temp. Mine said it was only good to ZERO, it was -20 on my way to work. It was freezing up at highway speeds. Once you stopped the heat soak of the engine warmed everything up.
To fix this drain out what you can and add more radiator fluid and recheck.

 

maybe your thermostate might e bad and is in need of replacement as said above