I recently bought a very nice 2000 NB with 35,000 original miles. One owner, with every receipt from new. But it's 22 years old so I decided to bring all maintenance items up to date. I have fitted an Ultragauge, which plugs into the OBDII connector and gives all sorts of information. I was disappointed to find that the car normally runs about 205 degrees--and even tops 210 (I have a warning set) before the thermostat opens for the first time. I decided that this wouldn't do. I think Mazda selected a 195 thermostat--back in the day--mostly for emissions considerations. But it's my personal opinion that these very hot running temps are chiefly responsible for all the tan colored radiators that need replacement. Anyway, I changed all 7 coolant hoses, both serpentine belts, and installed a 180 degree thermostat from Moss Miata (part number 999-026, for $7.99). I am now running 185 degree temps, instead of 205, and I am very happy with this. By the way, the stock temperature gauge is useless. The needle shows the same for any temps from 180 to 220.

On another matter, I took off the so-called 'under cover' plastic valence which covers most of the under engine compartment. I have no idea why this is fitted. It can get caught on curbs, etc. and rip off the front fender support. This has happened to friends. It did hundreds of dollars damage. I had run it on my 1992 because I couldn't run the Ultragauge to see temps (it didn't have OBDII). But now I can tell you that it makes absolutely no difference to the engine temps. If you do break down somewhere, and have to change the bottom radiator hose, you have to take this off. Good luck doing this by the side of the road somewhere. I'm not running it anymore.