Saki GT

I've noticed during this colder weather that my transmission is actually shifting smoother during the intermediate period between cold and fully hot, and I assume it is the particular oil viscosity while its warming up. Currently I have the Honda MTF.

Can we go to a slightly heavier transmission fluid without issues? Thoughts?

SpitfireS

Honda MTF and IMO most MTF's are - whatever the name is - gears oils in the SAE 80 range, between 7 and 11 cSt.
In the temp range your trans shifts best I guess - by looking at the Amsoil MTF specs JUST because they are easy to find - the oil could be around 25-30 cSt. @ 50C.
All ballpark & just guessing numbers.
Amsoil MTF is 47 cSt @ 40C.
Its possible to calculate but I am lazy.

Anyway..
A gear oil that would be 25 cSt @ 100C is an SAE 110 / 140

I'm not sure there are GL-4 (no GL-5!) manual trans / sychromesh oils available at that viscosity.

The only one I know is the famous LE-607.
That oil was IIRC non (or very little) corrosive to yellow metals eventhough it was a GL-5 oil.

Using those oils (SAE 110 / 140) could mean it may shift pretty hard at lower temps.
And it will use more fuel.

Main thing is to find a GL-4 manual synchro trans oil in SAE 110.
I've never seen any.

s2k dre

Wouldnt heavier fluid make it shift a little rough in this cold?

speedworksracing

I run strait Redline MT90 in my car.

It SUCKS in the cold, but it is butter when it warms up.

I have heard it is better in cold weather to mix MT90 and MTF together but it is only cold here for 2 months or so and even then we only get 2 weeks of really cold weather.

ahrmike

Speedworks, what do you consider "cold"?

Emil St-Hilaire

Redline MT-90 FTW...

Saki GT

With 56k mi on the car, I've noticed that there is some "tumble" into gear no matter what now, but a warm trans that is warm enough not to be notchy yet cool enough that the oil is still thick seems to be the magic point where the car shifts the smoothest.

I've run Honda and GMSFM and the GM stuff is very smooth, but has a short life. I think years of a voodoo knob and gear shifting has put some wear on the synchros to the point that they don't have the rifle-bolt smoothness that they had when new, but they are no worse than the shifter action I've experienced in other S2000s.

I think I will try the Amsoil on my next change.

SpitfireS

Saki GT Posted on Jan 14 2010, 07:09 AM
I'm using the ATM now and I like it, smoother than GMFSM.
Time will tell, so far only 2500 km.
But ATM is only 9.6 cSt.

The Redline MT-90 has specs closer to what you are looking for IMO.
So does the Amsoil MTG (75W-90 GL-4).
Redline does not specify the ASTM Copper Corrosion Class, I'm sure its the same as the Amsoil MTG, being 1B.

All in class 1 are safe IMO.

camuman

OP lives in NC, running straight mt90 will suck in the cooler months, esp winter. notchy FTL. i run MTL, its 75-85 i think. works well even when it was 40 degrees down here. lasts about 10k miles at the most though.

speedworksracing

Well it is 50 degrese out now and I am wearing a jacket, gloves and a beanie.

It was in the 30's here last week though, I thought I was going to die.