Bert

I'm thinking I will change all the fluids in my '10 GT this spring. I know it probably won't make much difference, but hoping to make the tranny shift a little easier in cold weather, reduce friction to minimum possible, maybe pick up a fration of a MPG and/or HP at the rear wheels, etc.

What is the "best" synthetic transmission fluid for the 2010 5-speed? (I'm not sure if the 2011 6-speed might be different)

While we're on the topic, how about the differential fluid? What's the best stuff to put in there to reduce friction, etc.?

Ltngdrvr

Just go with the spec in your owners manual.

I believe the tremec manual tranny on a '10 calls for mercon V which is a synthetic.

And the 2011 is completely different spec for the tranny fluid.

Rear axle is 75w90 and go with a synthetic there too and don't forget the friction modifier.

Knight

GM synchromesh

Bert

thanks for those replies so far

I was hoping for something "better" than the stock fluid, specifically with respect to stiffness in cold weather -- wondering if there was something else out there that would not thicken up so much in the cold. (assuming that is the reason the shifter is so stiff when it's cold)

On another forum, somebody replied "I called Tremec and they recommended Mobil-1 ATF" -- any thoughts on that?

godspunk32

I'm planning on doing this in my 2006 manual GT, as well. What do you guys think of the Royal Purple Synchromesh and gear oil that Brenspeed sells?

JR

David Young

I used Royal Purple motor oil in my last car (Dodge). I read several test and the RP gear and rear-end lubs didn't do all that great. So you might want to do more research on the internet. I'm sticking to Motorcraft for all my lubs.

Bert

Researching this some more, I learned that "Mercon V" is a specification not a product, and the Mobil 1 ATF meets this spec.

The Mobil 1 LS (for limited slip) gear lube looks pretty good too.