As the title asks, what's your preferred magical oil for a 5-speed Miata NB transmission? I'm going to drain and refill one of these days . Car has 120K miles on it and I'm assuming it's the original oil in it now.
As the title asks, what's your preferred magical oil for a 5-speed Miata NB transmission? I'm going to drain and refill one of these days . Car has 120K miles on it and I'm assuming it's the original oil in it now.
Can't go wrong with Redline MTL. Don't forget the turret oil and new shifter boots.
Ford mtf.
I had the unknown oil in my '99 replaced with Redline MTL a couple years back during a clutch job. I was hoping it would help with my slightly crunchy 1-2 and 2-3 shifts, but unfortunately I didn’t notice much if any difference.
I’ve heard good things about the Ford/Motorcraft XT-M5-QS, but I can’t bring myself to drain & waste the MTL just yet :)
I've used Redline MT90 and Ford/Motorcraft XT-M5-QS in my RX7, which has essentially the same transmission. Other than the higher price point of the Ford/Motorcraft oil I didn't really notice any difference between the two. The 6 speed Miata guys rave about it though. For Redline I always thought MTL was too thin (75W80) and that MT90 (75W90) was the correct weight. I wouldn't expect miracles. Nothing is going to fix worn synchros or bad bearings but going with any high quality, synthetic GL-4 oil is going to be better than what's in there now.
therieldeal said:I had the unknown oil in my '99 replaced with Redline MTL a couple years back during a clutch job. I was hoping it would help with my slightly crunchy 1-2 and 2-3 shifts, but unfortunately I didn’t notice much if any difference.
I’ve heard good things about the Ford/Motorcraft XT-M5-QS, but I can’t bring myself to drain & waste the MTL just yet :)
I switched from Redline to the Motorcraft unicorn tears and the improvement was dramatic, much to my chagrin. It really is worth the extra money, it was a night/day difference in how the car shifts.
Ford MTL was the hot ticket many years ago, don't know if that's the case now
I've tried the Motorcraft, and agree with Infernosg, it's great, but it's not better than RedLine MT90. I've used MT90 primarily for the past 20 years with good results.
I will say that I was not impressed by Mobil1 75W90. I had a rear transmission seal fail and dump a lot of fluid once and I needed something in a hurry so I grabbed the M1 off the shelf. It was significantly more notchy than the RedLine, and switch back a short time later made it smooth again.
I've also been less than impressed with Royal Purple. I had a car I temporarily owned that the syncros were going out on like thereildeal (drivable but notchy), and I figured I'd spend the big bucks on RP. It was about as bad as the Mobil 1, so I switched it out to RedLine before selling it.
I've run Redline MT90 and Motorcraft XT-M5-QS in my '91 Miata. Either one is way better than the original fluid. On a cold morning (< 40°F), the first few shifts with Redline are a little notchy/stiff until the trans warms up. First few shifts with the Motorcraft are always smooth no matter the temperature. Other than that I haven't noticed a difference between the two.
MT90 is a good option for hard working transmissions as long as you can give it time to warm up. MTL has been the go-to for street Miata transmission for 30 years.
In reply to Keith Tanner :
It's a street driven, supercharged NB, never tracked or autocrossed so sounds like I need to find the MTL then.
In reply to thatsnowinnebago :
I did the turret refresh last fall, but the oil I used was likely Mobil1.
FWIW I use MT-90 because while people having been using MTL for decades without issues, it doesn't actually meet the specs that Mazda calls out in the owner's manual.
I've tried the cheap stuff, I've tried the Redline, I've tried the Lucas. I'll be damned if I could ever tell a difference.
I used Ford/Motorcraft XT-M5-QS in both my '99s and loved it. In my second one it helped a lot with the abused 3rd gear synchro.
A friend recently bought an NB ( 5speed) that had just had the transmission changed with some flavor of Redline. He complained about it being very "crunchy". I suggested a change to the Ford fluid and he was pleased with the change. His issues went away.
I know some people swear by Redline, each to their own. I prefer the Ford fluid.
Ford/Motorcraft XT-M5-QS feels better than Redline in a Miata transmission, having experience with both. Worth my money and Rockauto sells it for much cheaper than dealer. There is always a 5% off promo floating around the forum as well.
https://www.rockauto.com/en/parts/motorcraft,XTM5QS,transmission+fluid,13630
Anyone tried the Honda MTF in a Miata transmission? It was recommended for and worked wonders on my Saab C900. As a new ND owner who just turned the first 1k miles, I nonetheless feel the need to plan ahead.
I have used both Penzoil syncromesh and the Redline MT90 in the 5 speed Miata box.
Syncromesh probably wasn't a good idea because its quite a bit lighter weight than what Mazda recommends. Shift performance was great initially but seemed to degrade after a few thousand miles.
The MT90 felt the same as the Syncromesh but the shift feel stayed the same after 15k miles.
My trans was crunchy and hard to get in to second gear so I put the Redline fluid in, with no change. So I decided to try the Ford unicom blood and it feels like a new transmission no more grinding and second gear shifts like a charm.
I've tried everything except Royal Purple in the RX-7 version of this transmission (I haaaaate that stuff) and I came to the conclusion that any benefits of MTL, MT-90, GL5, OMG etc. were placebo effect. So I just get whatever gallon jug o'gear oil is cheapest at the parts store, maybe cut it a little with some leftover ATF.
Pete. (l33t FS) said:I've tried everything except Royal Purple in the RX-7 version of this transmission (I haaaaate that stuff) and I came to the conclusion that any benefits of MTL, MT-90, GL5, OMG etc. were placebo effect. So I just get whatever gallon jug o'gear oil is cheapest at the parts store, maybe cut it a little with some leftover ATF.
My FD arrived with a transmission that was really balky and hard to shift, I had read that their synchros were somewhat fragile, so I started looking for a replacement. Before I got around to doing anything about that though, I needed to replace the clutch, which meant changing the fluid. Drained out some fresh-looking fluid that the previous owner had put in, replaced it with Redline and it was night and day, all of a sudden everything worked properly.
I have no idea what was in there, but whatever it was that transmission hated it.
Another vote for the Ford MT fluid. My MSM had a balky second gear synchro, so I tried Redline MTL. It was better, but the old Mazdaspeed forum recommended the Ford stuff. While it doesn't shift like a 5-speed, it's definitely better with that oil.
In reply to codrus (Forum Supporter) :
The FD had an updated version of the RX-3/4/5 transmission, which had a reputation for finicky synchros. Those were REALLY fragile, they had built in stress risers and could bend with one poorly-executed shift!
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