Tranny Fluid - Redline MTL vs. MT90?

Dave80GTSi

Dave80GTSi

Original Owner 1978 X1/9 (now sold)
Yes, I did a search on this topic, and found lots of round-about discussions, but not much on this specific point:

What's the difference between Redline's MTL and MT90 transmission lubricants?

And what criteria should a fellow use in order to select one over the other for use in our X trannys?

Any specific pros and cons concerning these two types?

Thanks - DM
 
Having not tried MT-90, I do have MTL in my X and have found a noticeable improvement in shifting as well as overall smoothness.
 
As I understand it, MTL is Lighter and MT-90 is heavier.

So it's probably safe to say:

MTL would be good for cooler climates or car usage that could be characterized as occasional spirted driving, semi-daily driver, weekend driver, show car, etc.

MT-90 would be good for always hot climates, regular spirited driving, everyday daily driver, occasional autocrossing.
 
The PRO... is Steve Hoelscher...

... as he rebuilds them and races them and everything else.

If I may summarize HIS words... he recommends the MT90 for racing and either for the street.

MY words are... install 4 quarts of MTL and you'll never regret it. Like an overhaul in a can... Give it a few hundred miles and you'll agree.
 
From www.redlineoil.com

MTL is 70W80 and MTL-90 is 75W90. I put MTL-90 in my transmission because 75W90 was closer to the fluid spec. in the service manual.
 
MTL vs MT90

Bascially, all of the above is correct. MT90 is + 5 - 10 points of viscosity. That's it.

If you live in a very hot climate and/or drive your car very hard, I would go with MT90. I recommend MT90 for my racing transmission customers.

I used MTL in my autocross cars for the last 20+ years. It works great. I also use MTL in my street X and it gets driven in Florida heat. Works fine.
 
Interesting!

OK, I just went out to the garage and pulled my old blue binder factory service manual down off the shelf.

There the OEM factory spec calls for SAE 90 weight lubricant.

Based upon the weights of the MTL vs. MT90, looks like the MT90 better meets the 90 weight spec, so there you go!

Thinking about this one a bit more, could it be that those folks who claim that their tranny shifts "better" when filled with fresh MTL Redline fluid are actually reacting more to the use of the lighter weight oil, rather than some mystical chemical properties that Redline offers and that other oil brands do not?

Under this hypothesis, any given brand of oil would allow the tranny to work just the same as another, so long as the viscocity of both fluids are kept equal.

( ... not trying to justify a switch away from the use of Redline here ... just wondering out loud as to why Redline has earned such a fine reputation).

Maybe I could do a 50/50 mix of MTL and MT90, which would give me a viscocity more or less in the middle ... the best of both worlds ... ?

Thanks to all - DM
 
Dave... NOPE... MTL and MT90 are formulated...

... for TRANSAXLES and not just transmissions or rear axles. They also have what I call "abrasive" qualities so that the syncros will more easily align and shifting becomes smoother.

I can't tell you why the gear selections appear "notchier" but they do... more definate and concise. I've LIVED OUT and experienced the differences on several transmissions, and apparently, others here have also become believers.

You can definately experiment on your own at some cost or take advantage of our learnings. In fact, if you're willing, I would encourage it. Steve Hoelscher himself tried straight ATF at one time and found it worked well... but the extreme abrasive quailities in ATF (for clutch adheasion) did a number on the gears themselves, relative to wear. HA! I appreciated his attempts... and am gonna just take his word for it... HAHAHA!

Let us know what ya find...
 
Nope

Dave,

It's not a function of viscosity-- Redline uses special friction modifiers to cause the synchros to mesh more smoothly. Been years since I've looked, but there used to be some technical info on their site that explained in some detail.

I found MTL around 20 years ago while trying to solve some crunchy gear engagement problems in a BMW. It solved the problem so well that I've been a Redline fan ever since. It ain't snake oil. It's an engineered product.

Several here, including myself, have used motor oil in X transaxles, often in lower viscosities than MTL. Bur MTL works better, regardless of weight. It's one of those rare products that works as claimed.

IIRC, Redline says flat out that the only difference between MTL and MT90 is the viscosity/intended temp range. Like Steve says, if the car is driven hard or lives in a hot climate, MT90 is prolly a better choice. But frankly, we've run MTL in BMW race cars where the trans tunnel actually gets too hot to touch in the summer, and never seen a problem.

Where I live I'm a fan of MT90. But if you drive your car when it's cold outside MTL would likely be the best choice. If you have any doubts just call Redline-- I'm sure they'd happily advise you. In any case, you won't be regret installing either MTL or MT90.

HTH,

///Mike
 
The Facts

Dave80GTSi said:
There the OEM factory spec calls for SAE 90 weight lubricant.
Click to expand...

This is the one time I will tell people to ignor the FSM. Lubricant technology has come a very long way in the 40 years since this transmission was developed. I have tested almost every reasonable option for lubricants in these units. Everything from ATF (as Tony mentioned), motor oil, various app specific products to straight 90 wt. I use MTL.



Dave80GTSi said:
Under this hypothesis, any given brand of oil would allow the tranny to work just the same as another, so long as the viscocity of both fluids are kept equal.

( ... not trying to justify a switch away from the use of Redline here ... just wondering out loud as to why Redline has earned such a fine reputation).
Click to expand...

I understant your skepticism. I am a skeptic myself. However, as I noted above, I have tested MTL and MT90 along with most every other practical alternative. MTL/MT90 works way better than the vast majority of the alternatives and only a very few approach MTL/MT90's level of performance.

I estimate that I have built more X1/9 transmissions than anybody else I know of. Even most Fiat technicians wouldn't average one a month over their carreer (of maybe 20 years tops?). I have been building these units for about 25 years now. In addition to that I learned alot about lubricans in the 8 years I owned and operated a big AAMCO Transmission Center. Not to mention that I worked for a Pro race team for which Redline was a major sponsor. In that capacity I worked directly with Redline engineers on our racecar's oil requirements. I know first hand that MTL and MT90 are the real deal.

Dave80GTSi said:
Maybe I could do a 50/50 mix of MTL and MT90, which would give me a viscocity more or less in the middle ... the best of both worlds ... ?
Click to expand...

Don't do that. Viscosity differences don't work that way. And there is no "best of both worlds". If its a street car, put MTL in it. It works in my high HP street car just fine. I also run MTL in my 200 hp MR2.
 
I run MTL in both my X's

Done purely from the advice from this Web site, (and Steve) and I can honestly say all has worked fine since. Shifting improved noticeably in my 86X.
 
Question

Wow, happy that this subject came up. Ok, I got my car back from Robert at Shadetree several weeks ago where one of the jobs performed was to put MTL in my X. Well, it was and I must say I can see an improvement. Problem is my tranny is leaking now. I know the MTL is synthetic and lighter and that could be a problem, but my tranny was rebuilt no more than maybe 8K miles ago. I think Jason Adamski had Mad Matt do the rebuild on it. Anyway, it's not pouring out or anything, but it's definitely dripping. My question is, is there some sort of "additive" maybe to put in there to stop that without taking away from the fluid itself? I'd hate to have to drain that MTL out of there and use something else.....that stuff wasn't cheap :p
 
Mine did the same thing but

got lucky... just a matter of tightening up the 10/12mm. bolts at the housing as tight as you can go.
 
Additive

The only thing I'd add is a new gasket to fix the leak.
Pouring in something that would "clog" the hole can only screw up the (expensive) oil formula you've invested in.

My opinion only.
 
SciFi65 said:
Wow, happy that this subject came up. Ok, I got my car back from Robert at Shadetree several weeks ago where one of the jobs performed was to put MTL in my X. Well, it was and I must say I can see an improvement. Problem is my tranny is leaking now. I know the MTL is synthetic and lighter and that could be a problem, but my tranny was rebuilt no more than maybe 8K miles ago. I think Jason Adamski had Mad Matt do the rebuild on it. Anyway, it's not pouring out or anything, but it's definitely dripping. My question is, is there some sort of "additive" maybe to put in there to stop that without taking away from the fluid itself? I'd hate to have to drain that MTL out of there and use something else.....that stuff wasn't cheap :p
Click to expand...

Don't use any additives. If the transmission had 90wt in it and you converted to MTL, I am not suprized it is leaking. The synthetic molicule is quite a bit smaller and will leak where 90wt won't. The fix depends on where its leaking from. A gasket or seal?

Also, assuming it was indeed a rebuild from Matt, depending on when it was done, it could have been one of mine. If so, and it had 90wt in it, then whoever filled it defied my recommendations. I put a sheet in every transmission I build specifying Redline MTL or MT90 ONLY.
 
Thanks to all!

To re-emphasize: I'm not trying to re-invent the wheel, nor to stir the pot on what appears to be a topic that a number of folks hold dear.

Just being curious.

Thanks - DM
 
Wait!

Greg (in Conn) said:
got lucky... just a matter of tightening up the 10/12mm. bolts at the housing as tight as you can go.
Click to expand...

The spec for those bolts is 18 lbs/ft. "as tight as you can to" will likely strip the aluminum case threads and create a bigger problem.

Tighten them to spec. If that doesn't stop a case leak, then you need a reseal.
 
I'll look and see if any documentation came with the car concerning the tranny Steve. Not 100% sure, but could have swore I saw something stating it was rebuilt at Matts joint. From what I recall it was done around 8K or so ago, may be a little more or less. I'll crawl under there and see exactly where it's coming from this afternoon and repost. Like I said, it's not pouring, but after sitting several days it's enough to create a saucer sized oil spot. I also see where it hits the tailpipe and runs down, about where the CAT should be (my X doesn't have a CAT on it).
 
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