Originally Posted By: k24a4
I use 5w-30 in my '93, Redline MT 90 in the transmission and Redline 75w-90 gear oil (non-friction modified) in the differential. Don't forget to check the turret oil when you change out the trans fluid. Mine was low when I got it in 2007 @ 95,000 miles. I replaced the boots as well. As others have suggested, a great resource is
http://miata.net/. Replacing the clutch slave is a great idea, as well.
Great car. Happy motoring.
MT 90, that's the stuff! Works great, very smooth shifting unless it's very cold out, then it can be a bit notchy at first. Also put in the same tranny oil, which I had forgotten about until I looked back in my little maintenance notebook. I also had to change out the slave when we first got it. It's a cheap thing to do and worth it if the shifting isn't as it should be all the time.
+1 on the turret oil. Many folks don't even know it exists.
As for running 10w-30 in the summer, of course it isn't necessary. But if you're like me and had some already on my shelf, it is perfectly fine and spec'd in the manual for "hot" temps.