MTL selection for a M5R1 specifying Mercon 3

Nov 17, 2015
I've got an mazda M5R1 transmission sitting here.
Ford ranger trans, Ford specifies Mercon 3.
First is really low, big change to second, lots of work for that synchro. I put bearings, synchroes, and sliders in the trans. Gears looked great, most of the bearings looked fine but some races had some synchro material impingement.

I Ran it the last 40k miles on valvoline maxlife.
Which until now I didn't realize was a pretty light fluid 5.9 cst @ 100,
Gears and bearings didnt appear to suffer.

This trans supposedly needs a thinner fluid like mercon 3 7.3cst as the oiling layout requires it and ive heard some of the needles will lack supply without it. (Its got a little plastic impeller scooper on the shaft that forces fluid down the shaft and out some holes in the shaft to some of the bearings.)

The trans worked relatively fine, but I want a FAST 1-2 shift, it was the entire point of taking it apart. I'd like to maximize the shifting properties.

I'm thinking with thinner oils the synchro can wipe the oil off faster, but Im not sure this is a fact or fallacy.

The trans seemed to wether fine with 5.9cst cheap maxlife.

I was looking at RP synchromax, then RL MTL,
Then Redline MTLV.
I like the idea of the MTLV its thinner than mercon 3, but thicker than the maxlife, and the FM package should allow it to outperform ATF as far as synchro performance goes.

So I'm looking for suggestions, advice, ideas...

Ps I called redline and he was trying to steer me towards d4, even after I told him it survived on 5.9cst oil.
Dec 22, 2002
The Garden State
I had the Mazda 5 sp manual tranny in my 2002 F-150. It spec'd Mercon which it shifted terribly with. I used RP Synchromax and it improved it a lot, not perfect but much better. Also used that i my 1996 Contour with the MTX 5 sp. It didn't make a noticeable difference in shifting but it has the better additives for a synchromesh transmission versus ATF fluid.