I switched to Syncromax at around 60K miles on my Ranger because the shifting was not as smooth as I prefer it. I noticed with the Syncromax the smooth shifting came back and I was very happy with it. After about 60K miles on the Syncromax, the shifting became not as smooth again. My experience with synthetics is once you switch to it you are good to go for a very long time. I let it go, thinking the trans was just getting slightly worn.
I am getting ready to tow my race car round trip from So. Cal. to Wisconsin and decided to change the trans fluid. I went with Syncromax again and immediately the smooth shifting came back. It looks like with the way I use my truck, I need to change trans fluid every 60K miles, synthetic or not. I suspect this kind of change interval (or sooner) would be good for all manual trans Rangers (with the Mazda trans).
2002 FX4 Bright Red Supercab 4.0 SOHC, manual 5-spd & Tcase, 33" BFG MTs, K&N air filter, Modified air box inlet, Gibson SS cat. back exhaust, Bama flash, Hidden Hitch round receiver, Rear helper air springs, Electric trailer brake controller, Line-X bed liner, WAAG bar with KC lights and Wildernest shell.