zeroptzero

I actually should correct myself about viscosity concerns. I've owned a couple high horsepower cars that put down 50% more power and 100% more torque than this S2K, and they came from the factory spec'd with ATF fluid in manual trannies.

Bror Jace

Yes JFusion, some trannies behind high-horsepower V8s recommend ATF for a lube. I'm not sure why ... machining tolerances, I suspect.

You can see INDYMAC's Honda MTF II VOA here:

http://www.bobistheoilguy.com/forums/ubbth...039#Post1971039

With the reformulation, the viscosity went from about 10-10.5 down to 7.5 and I suspect this is for a slightly improved shift feel and to reduce hydrodynamic drag and improve fuel economy a fraction of a percent (similar to the switch from 5W-20 motor oil from 5W-20.

INDYMAC, good luck with the Schaeffer 10W-30 ... I'm actually surprised that it is working as well as you say it has. friction modifiers can go both ways ... up or down. Really slippery oils can make for balky shifting as they can hamper proper synchro engagement. I used Mobil 1 10W-30 in a 2nd Generation Acura Integra a couple decades ago ... was terrible and I drained it after a month or two in favor of Red Line Oil MTL.

Aren't the AP2's synchronizers sintered carbon? I think that's what's listed in the Wiki entry for the S2000.

zeroptzero

Bror Jace, thanks for the information. I always thought Honda MTF viscosity was in the low to mid 10's (100 CST), but I guess that changed with Honda MTFII. That explains the lower viscosities we are now seeing.

I honestly believe thicker is better for the differential on this vehicle (given certain operating conditions), but I'm not so sure that applies to the tranny. My last two vehicles changed my mind about thin transmission fluid, at first I thought it was blastphemous, but tons of guys on our forums abused the crap out of those vehicles and tranny failures were rare , even when guys doubled the hp from factory setups. - i.e. - upwards of 500 whp. - on ATF.

I'll try to take some fluid samples from the tranny and diff. in the coming months, in addition to my crankcase sample. Currently running Amsoil 5w40 in the crankcase, Honda MTF2 in the tranny, and Amsoil 75w-110 Severe Gear in the dif.

thanks for the great info in this thread

INDYMAC

Well, I just get back from a longer test drive than yesterday. It took about a mile of 20MPH residential roads with stop signs to get to a main road. The 1-2 shifting felt different than MTF II, but not bad. A little more force required, and 2nd gear only balked once on a low RPM shift. MTF II results in the same thing sometimes.

Once on the main road I found a good pace truck to follow at 68MPH until I got to a road I wanted to turn off on and flog the car for awhile. Speed Limit was 70MPH with lots of tight turns and long sweeping high speed turns. Lots of up-shifting and downshifting for about 10 miles, some rev matching and some not. The tranny shifted great until near the end. It started to feel a little different (mushy?). It was 97F outside air temp.

At the end of that road I turned south for about 5 miles and just let everything cool down some. Then I headed east on another road I like that is very similar to the last, only more bumpy. I let'er rip again with no problems shifting.

Here's what I summarize so far, but my opinions may change as I get more seat time:

-The 10W-30 reminds me very much of MTF I.
-I won't say it is useless or terrible (the AMSOIL MTF/MTG mix I tried was in this category), but it doesn't seem perfect either. I'll put it in the "good category" for now.
-I think it might be better than MTF II for a long hot Texas summer. But MTF II might go back into the tranny in the fall.
-The only rough spot for me (and many others on this board) is the 2nd gear shift at lower RPM's when the fluid/tranny is not warmed up yet. I think the 10W-30 handled this better than MTF II, at least on this run.
-I sensed some power loss with the 10W-30 instead of MTF II.
-It seems easier to find the gears with 10W-30.

Bror, I'm pretty sure that the AP2 synchro's are brass covered with a layer of carbon fiber. Maybe one of the Techs can weigh in on that topic.

Bror Jace

For the diff, I'm still trying find someone who will ship me a couple quarts of Chevron Delo synthetic 75W-90. Waiting for responses to e-mails sent. If that doesn't work, I can find Lubromoly locally for $10 per quart ... but I'm dying to try Chevron's borate chemistry.

Yes JFusion, it seems wearing out a tranny is rare. Failures are usually pretty extreme examples ... someone putting hundreds more horsepower (or more importantly torque) through a tranny and having a catastrophic failure.

Typical abused trannies pop out of gear, howl, etc ... and I'd like to avoid that if I can.

I come back to the idea that the Honda trannies in existence were designed to be lubricated by something like a 30 weight motor oil ... albeit with a tweaked add pack including syncro-friendly friction modifiers (I think MTF II became available in late 2006). ... so after I dump my Honda MTF II, I'll get some Amsoil MTF ... which works well in my Civic and is very close to the original spec viscosity. If I end up going that route, I'll get it and some Amsoil Severe Gear for the rear from Pablo.

"The only rough spot for me (and many others on this board) is the 2nd gear shift at lower RPM's when the fluid/tranny is not warmed up yet."

This was the thing that gave me pause about the quality of the tranny when I first started driving the car. Good to hear it doesn't happen as the speed/revs climb. I notice there's a difference in the shift quality when the car's been running for 15-20 minutes ... which is good.

zeroptzero

The previous owner of my car had Redline MTL in the tranny and it was changed regularly. I didn't like the way it shifted when I got the car and changed it over to Honda MTF2. With the previous Redline fluid it had a noticeable crunch feeling when shifting into second, it just wasn't smooth and it happened quite often on a regular basis. Ever since I changed over to Honda MTF2 it has shifted perfectly and the previous issue has never returned. The difference was immediate and very apparent with no other changes made. Perhaps my tranny likes the thinner Honda fluid as Redline MTL is a bit thicker. I always regarded Redline as a great tranny fluid but it didn't feel good in my tranny.

INDYMAC

Picking a tranny fluid for the S2000 is very subjective. There are many right answers, and many wrong answers, even for the same MY. That's the only thing I know for certain about MTF's after studying it for the last almost 7 years now.

zeroptzero

I'd go even further to state that the change is likely verhicle to vehicle, probably depending on the wear of each tranny and what viscosity works best with the tranny. Driver sensitivity may have something to do with it as well.

INDYMAC

I took another short drive today (25 miles). It was about 94-96F outside and sunny. I didn't try to perform any acrobatic feats this time. But I'm getting more comfortable with the 10W-30 in there and I'm shifting more confidently. I'm not worried about whether I made a mistake or not anymore. It doesn't feel as easy to shift as MTF II, but the shift feels sure and good. The tranny doesn't feel as fragile and temperamental as it was getting to feel with the thin MTF II, especially 2nd gear. I'm wondering if the higher HTHS of the Schaeffers oil isn't helping the synchro's accept the shift, or maybe the additives are helping to heal my getting worn 2nd gear synchro's.

Anyways, all is good so far...but still early.

slipstream444

Amsoil MTF with 95-100F southern heat - no problems.
The trans is smooth from start to finish.

In the colder months I typically have to double-clutch from 1st to 2nd and from 2nd to 3rd for the first couple of shifts - when the temps get into the 50's F. I have to do this regardless of whether I'm running Amsoil MTF or Honda MTF II. Summertime temps - that's not a problem.

INTJ - mixing two very different fluids is never a good idea. They may be "compatible" - but that certainly doesn't mean they'll work together beneficially.
Amsoil specifically states that you loose all benefit of their fluid if you mix it with other fluids. Their tech services specifically state it's not a good idea, and Amsoil will not warranty against oil related failures if their fluid is mixed with another fluid.
So unless you're a chemical engineer that's done extensive tests - and know exactly what you're doing - it's a bad idea.
Additive packages many times do not compliment each other. Stick with one fluid.