Transmission oil question
 

Hi, I have done a lot of searching. I found a lot of info on tranny oil, but nothing on this oil.
I was thinking about using the Motorcraft XT-M5-QS. Reason is that it is a really good oil and it makes a huge difference on the Mazdaspeed 3 6 speed tranny (I have a 2013 Mazdaspeed 3 as well).
I did some research and it seems that it would work for the RX-7 transmission (in terms of specs - it can be used in a GL-4 tranny, which I understand is what the FD has and the grade is 75-W90). My question is whether or not anybody uses it, or anybody would advice against it for whatever reason I am not aware of and wasn't able to find through searches here or on google.
Thank you for your contributions.
Giovanni

Try it and report back! ;)

It should work fine and apparently is use quite a bit in the Miata realm.

Thank you Mahjik, I always appreciate your insight. I'm always paranoid with this car and so I'm always expecting that when I think I've covered all the angles, there is still something that somebody who's more knowledgeable than me has thought of and that I missed.

It is used a lot on the Speed three due to its ability of "transforming" the transmission shifting smoothness, so I thought it might help with the FD. I have to change the oil, so I'll give it a shot.
Giovanni

I agree - it should work fine.

Generally I have my doubts that there is any real difference between the premium transmission gear oils, but this looks to be a good choice.

I should be able to put it in later into next week. I'll certainly report my findings (if there will be any...).

Interested to hear the results.

UPDATE (actually, not really, but I had to post this as I'm really pissed).
 

I called Ford today. I asked them for the above mentioned transmission oil.
I gave them the part number: XT-M5-QS.
They told me they had loads of it, just come over any time.

So, after work, I did. I stopped there and I repeated what I needed. The guy comes back with bottles that say "Automatic Transmission Oil". So I say to him: are you sure this is what I asked for? It says Automatic on it. He says something like "it is also for manual trannies" and what not. I look at the bottle, I can't see where the part number is and I'm in a hurry because I have another 2 stops to do and tomorrow I have to go teach 2 classes, drive 1 hour to a funeral home, stay there for a bit, then drive my wife back, pick up another coach and then come down to pay a visit to you fellow Americans as the team I coach is in a tournament in Columbus this weekend.

Once I got home, I went back on my computer and investigated a bit, got a bottle from the trunk, looked harder and found that this oil is part number CXT-5-LM12.

You tell me how you get mixed up.

So, tomorrow, I need to add a stop to my routine. AAARRRGHH!!!!!
Sorry, I had to vent.

Oh the trusty guys at the dealer...

I live in Columbus, let me know if you want some good places to eat!

I certainly do! And thanks for offering the info. I'll find out where we are first and I'll report back this evening.
Giovanni

You can get it from Amazon and have a shop replaced the fluid. But it's quite expensive compared to Redline MT90, just saying.

Thanks for the info, I actually have the "Part 2" of my story, which is this:
I went back to Ford on Monday as I was in Ohio to win a tournament with the girls soccer team I coach. I get there, put the bottles they gave me on the counter along with the receipt and I say to them: "you gave me the wrong oil, this has a part number of xyz and I had asked for part number abc". So the guy calls the other guy, he goes to get the oil and when he comes back it is yet again a different one!!! This time we got way closer with the part number, but it was still not it. So I said to him: "look, it is supposed to be QS, not QSM. So he fiddles some more, tells the guy one more time and -third is a charmer- he finally shows up with the oil. I am shooting to put it in early next week, so I'll report then. I am extremely busy with coaching and my head is spinning.

BTW, I usually do this type of stuff at the school I teach, so it's free, whether I do it or my auto-colleague does it.

Back from the dead (sort of).
I managed to change the oil for the Ford stuff eventually and I've been busy with work, the RX7, coaching and family matters, so here is a late update on my experience.

The oil has definitely made a positive difference on my old and notchy tranny. In all gears (either going up or down), there is a much better feeling and less notchiness.

As a term of comparison, I have always felt that the tranny was pretty bad when cold and -although stayed bad- was better when warm. Now its operations are -when cold- better than before when warm. Once it has warmed up, it seems to have improved quite a bit.

The Verdict:
I'm happy with the improvement and I would recommend it, however, it does come with a steep price (for gear oil) and I do not have anything to compare it to (another synthetic, for instance), so I cannot vouch one little bit on this oil being better than another synthetic of your choice.
Would I do it again knowing the cost and the difference it made? Certainly.

I hope this helps.

Do you have any idea what the old oil was, or how old it was?

I can't remember either, to be honest, but it was quite old. I can tell you two things:
1) The tranny has always been like that for all the time I've had the car
2) The oil we took out looked green. I am not sure this helps in any way.

Keep in mind that I have driven this car since it's been in my possession for about 25/30K kms, so in terms of actual mileage, there couldn't have been much on it.

It makes sense that you'd see improved cold shifting, as the Ford fluid has a 40/100 viscosity of 76/15, where a premium 75w-90 ranges from 90/15 (Redline MT-90) to 119/17.5 (RP MaxGear).

Normally this would make me nervous about wear, but both oils maintain 15 cSt in the range of operating temps. The bonus you're getting with the Ford is slightly lower viscosity when cold.

Now one might think that 119 is very different than 76, but viscosity is a logarithmic property and so the difference here is still fairly small.