naishou

I would get at least a verbal guarantee from Castrol that it is OK. Here in Aus they have a free tech line that I called before using it in my S2000. The way they have written GL4/5 suggests that it should be but I wouldn't like to risk transmission damage and warranty issues. If you haven't already bought it maybe try Redline MTL first? I assumed you were in USA before (). I don't know what's easiest to get in Italy....

By the way, I just changed my WRX back to mineral (Castrol) GL-5 fluid and it shifts much better than it did with the Syntrax synthetic. Just goes to prove that synthetic is not always better for shifting even if it protects the gearsets better. It seems to take a bit of experimentation to find a fluid that is just right for a particular gearbox - even if it's the same model. Most WRX owners swear by Syntrax for example but it didn't work for me. Since S2000 gearboxes seem to vary so much anyway you may not like what another owner loves. Best thing is just to try it and see.

sixtynine

I asked about Redline but here in Italy nobody knows about it, I think I'll try with that Castrol TAF-X (as you can see on the label is an oil specific for gearboxes and I think that our transmission is mechanicaly almost like another manual transmission, so I don't really think this oil could damage something) anyway I'm ready to change back to Honda MTF

naishou

I think you're probably right. It's made for gearboxes so it should be fine. Let us know how it goes. You need about 1.6L by the way.

sixtynine

I tried with that Castrol TAF-X:
there is a little improvement regard the notching problem, my old oil was a bit worn, I don't know if that improvement there will be also with Honda MTF , anyway the car seems to shift more easily especially when the gearbox is cold.
My suggestion is this: if you want a better quality oil you can go with Castrol synt oil (synt oils are always better than mineral oils) but don't expect an important performance improvement.
I repeat: that's only my opinion.

Sixtynine