I have used both the Honda MTF and GMSMFM quite a bit and think both are good products. I will probably stay with the GMSMFM because it does help with 2nd gear notchiness when the transmission is still cold. I personally drive slowly and baby the shifts until the transmission is warm, so either product is acceptable to me. In fact, having grown up on manual transmissions without synchronization, it feels more comfortable for me to find gears when I shift if they are all a little bit notchy. BTW, would somebody please explain to me again why GMSMFM shouldn't be used with carbon fiber (AP2) synchros?

 

I switched from the Honda MTF to the GM stuff and I have to say that it is the best tranny fluid I have ever used...I track the car a lot and RARELY do I ever get any grinding. Back on the Honda Fluid I would grind a lot with less then 5000miles on the fluid. IMO they are both great fluids for the first 2500miles, but then the Honda sort of goes sour and the GM just stays great. I've had it in there for at least 10k miles now and its still good. Starting to get slightly notchy but I think that is because it is winter and 20 degrees out...not because of the fluid.

 

Now that I think about it, maybe it was the LE tranny fluid (parafin based) that was not compatible with the AP2. Sorry for the confustion.

 

A lot of this was put out in another post. However it's applicable here as well.

Using a fluid that is not specifically designed for a vehicle can, and in many cases WILL, void a factory warranty. Using GMSMFM in the S2000 transmission will void the factory warranty (if caught), and this is why:
GMSMFM was developed for the NV1500 transmission used in GM and Chevy 4-cylinder, light duty S-10 'style' pickups ... and NOTHING else.

Last time I looked, the S2000 didn't fit that description at all. I think it goes without saying the S2000 puts a lot more stress on a transmission fluid than a bubble gum, 4-cylinder Chevy pickup can.

Call GM, and without any hesitation they will tell you GMSMFM is NOT recommended, approved, or suggested for any application not noted on the bottle. This obviously excludes the S2000 from its use.
Call Honda, and they will tell you not to use any fluid other than ones specifically designed for Honda manual transmissions, and that meet the OE requirements set forth for your specific model. Doing so WILL void the factory warranty for the component involved - i.e. the transmission. I know this because I have made those calls.

Many on this forum have noted that GMSMFM has helped with shifting problems in their S2000. I've used it in the past as well. However, while it may have helped with shifting - it may be neglecting lubrication (especially at high RPM), or other key areas of concern. No one can say for sure because the fluid was not designed for, or tested for use in the S2000.

When it comes to the S2000, I only recommend fluids that are designed to specifically meet the requirements set by Honda. The only fluids currently on the market that meet these requirement are Honda MTF and Amsoil MTF. The latter is better for many reasons.
Amsoil MTF exceeds all of the requirements of Honda MTF, while incorporating a friction modifier package designed to meet the needs of GMSMFM (and other fluids). In fact, Amsoil MTF is listed specifically as a direct replacement for several fluids, including Honda MTF and GMSMFM.
No other fluid gives you all that. Not Redline, not Pennzoil, not Royal Purple ... no other fluid - period.
Amsoil MTF is also a FULL synthetic (GMSMFM is a semi-synth), is perfectly safe for BOTH the AP1 and AP2 transmissions, and cost less than GMSMFM. Amsoil goes further by covering components against oil related failures while using their fluids. Again, try to get GM to cover your transmission if it fails due to using their fluid.

I hope this info helps.

Use what you want to use. Recommend what won't get you sued.

 

Transmission manufacturers often give the option for either carbon or yellow metal synchros in the same transmission model line. The manufacturer will usually spec the same fluid for either type of synchro - this typically means there is no problem.
The rub is: I don't know if the NV1500 transmission was ever offered with carbon synchros, and therefore GMSMFM may not be compatible with carbon synchros. If the NV1500 was ever offered with carbon synchros ... then carbon synchro compatibility is probably not not an issue, unless GM specified another fluid for the version with carbon synchros. This does NOT mean I recommend GMSMFM for the S2000, because I don't.
However, read my post above before you decide to use any fluid. I will NOT recommend any fluid not specifically designed for Honda, this includes GMSMFM.

 

Just keep in mind Slipstream444 is an Amsoil distributor. That could be why he is so biased to Amsoil. I think Amsoil makes a great product but a lot of people have used the GMSMFM and Redline with great results as well.

No offense to you Slipstream but I think people should know why your post sounded like an Amsoil sales pitch.

 

Honda MTF works better for me.

 

I've been using GMSMFM in my '02 transmission for the last 50k miles and give it a . I get fewer 2nd gear grinds when the transmission is cold (compared to Honda MTF), but the difference in feel once the transmission has warmed up seems neglible.

Only reason I switched to GMSMFM is because I was getting more "cold transmission 2nd gear grinds" than I liked with Honda MTF. But if you don't have any problems with your current fluid, then I see no reason to switch.

 

I am an Amsoil dealer. No secret there. Your point seems to imply that I am making a pitch for Amsoil MTF because there's something in it for me.
Let me clear the air a little here:
I have not and do not sell any Amsoil product. I'm a Navy pilot, which takes up more of my time (ground job and flying) than you can imagine. I don't have time to peddle product.
Not withstanding the fact I'm currently stationed in the Middle East for the next two years, I still wouldn't have the time to sell anything.
I bought into a 'dealership' 7 years ago to keep from getting ripped off by greedy dealers.
I don't get any kickbacks or payment for "pushing" Amsoil. I don't have a brick and mortar or internet business. I just believe in the product based on scientific data and years of personal experience with the product.

I spent a lot of time (along with others on this site) to get Amsoil to make an aftermarket MTF for the S2000 - with the benefit of the friction modifier package - while keeping the factory warranty intact. It took over two years to convince Amsoil it was worth the effort to make the product.
Amsoil MTF benefits you. The only benefit I get from it is its use in my Honda.
It keeps your warranty intact, is a full synthetic, costs less than GMSMFM, has the benefits of GMSMFM - it's what so many on the site were asking for - what more do you want?

 

If warranty is not an issue for you and you've had good luck with a product - stay with what works for you.

However, if warranty is an issue (as in you want to protect your factory warranty), and you want a product that outperforms any other MTF on the market, has the benefits of being a full synthetic, and has a friction modifier package as in GMSMFM - Amsoil MTF is currently the only option.

It costs less as well. Skeptical or not ... what do you have to loose?