Here's how I would pick between the MTL and the MT90. If you have a heavy car
with lots of power, or a car that runs in very hot climates, or one where the
MTL has not worked well, then I would use the MT90. For anything else I would
use the MTL. I've used this stuff for 15 years or so and only had to resort to
the MT90 in a very few cases, mostly 3000+ lb cars with 300+ hp. I've used MTL
in trannys that called for light oil or ATF, trannys that called for motor oil,
and trannys that called for various viscosities of gear oil. The shear strength
of the MTL is higher than even a 140 weight dyno gear lube and it is only under
extreme conditions and hard usage that the MTL will be too thin. And the
advantage of the MTL is that it is thin enough to start working as soon as you
start driving, even in cold weather, whereas heavier gear oils will take a while
to warm up and get to their operating temps. The added ease of use and
protection from the MTL is a real plus. Not that the MT90 doesn't do better than
most dyno gear oils in this respect too, its just that unless you need the added
viscosity, why bother? The technology behind the Red Line MT series oils is
really remarkable. The synchros will work so much better with it than with
anything else. It sounds to good to be true and I was very skeptical when I
first heard about this stuff years ago, but it turned out to work just as
advertised.
The only problem I've ever come up with about synthetics is that they are so
slick they will not stick to parts at really high speeds. I no longer recommend
them for use in high rpm applications such as serious racing. I know of one guy
who runs a 1200 and lost a couple trannys using Red Line. His engine turns
around 10k rpm. Based on his experience, and some testing Don Potter did, I now
believe that the problem is the rpms involved. The stuff just won't stick well
at really high rpms. For any street application it is the best, but for some
race applications it is not a good idea.
"O'Farrell, Fergus" wrote:
>
> Okay, over-cautious with that warning. The RedLine site says GL-5 lubes
> shorten life, and both MTL and MT-90 are GL-4's.
> MT-90 is fine in my diff, but it wasn't making noise before, I just thought
> it was cheap insurance. Not so much leakage as seepage, which is okay by me
> as long as it doesn't spray on the poppy fields when I'm off-roading on a
> private road by the reservoir... (sorry, OT there) I haven't excavated the
> steering box yet, although from the price of them it'd be a good candidate.
> I'd go with the MT-90, as they say it is thicker than MTL. (not so runny
> thru any seal flaws). But you know what, 70-85W vs. 70-90W, I bet I
> couldn't pick them in the blind taste test. Fergus O
> -----Original Message-----
> From: Geegc@aol.com [mailto:Geegc@aol.com]
> Subject: Re: gear oil question/warning/ more Qs
> So you think MT 90 is a bad idea, and recommend MTL, or just stay with
> regular gear oil? If so, what weight?
> How is the MT 90 working in the diff? Any leakage? What are you using in
> the steering box?
> Gary C
>
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--
Marc Sayer
82 280ZXT
71 510 2.5 Trans Am vintage racer
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