Underheating?
 

yeah i know as soon as i ask about this my 13b will melt and the radiator will explode but it's really nagging at me. whenever i'm driving around on the freeway for more than a few minutes, my temp gauge needle is in between those two bars by C. other times it's almost to the middle of the gauge but not quite even under the same conditions. is this normal for the gauge to settle in different places like that or have i got some faulty wiring/t-stat/water pump issues? just wondering.

It might be a good idea to replace your thermostat (get one from the dealer, settle for nothing less than OEM) and invest in aftermarket mechanical gauges. It could be either one of those.

I would recomend using a quality aftermarket gauge to properly monitor your cooling temperature. The factory gauges are crap, and can't be trusted.

If your gauge is working correctly and your car is overcooling. Replace your thermostat with a Mazda OEM thermostat. Also check your fan clutch. When your fan clutch fails it will run constantly.

Good luck