I was looking to change the fluids in my '07 GT. What is the best fluid to use for my manual transmission/gearbox?

 

I went with redline mt-90 since that's what lots of people on the forum use.

 

OEM fluid, and change it every 30k. My original trans had over 143,000 miles on it and is still running in another RX-8. I only pulled it to switch to a Series II trans with 9000 miles on it.

 

Stick with one of the known ones:
- OE fluid from the dealer
- Redline MT90
- Eunos

Avoid Royal Purple, it's not the right type, it will destroy the syncros. Many other store available brands are just as bad. It's not worth experimenting with.

 

I highly recommend Ford Motorcraft XT-M5-QS. Best 75W90 GL4 manual trans oil available. Google it along with Mazda and you will see the praises ... does not have the cold shift balk like Redline. Can purchase any Ford dealership so likely local.

 

^ +1 on FoMoCraft oil. Been using it for a little more than half the ownership of my car. Very smooth, very easy shifts. No grinding no sticking when cold.

 

Cool, thanks guys