I have a 2008 Touring model 350Z with 6 speed manual.

My wife took it to Jiffylube to get and oil change and had them service the trans. It has 60K miles on it so I figured should be done. I don't know what kind of fluid they put in but now the car is a little stiff to shift, especially going into 1st and 2nd.

I'm going to check fluid level today but may change it out again myself. What is the best fluid to use? Factory Nissan or aftermarket?

most people prefer nissan oem its hard to beat, alot also like redline mt-85 which is what ill be trying out once i quit being lazy and put the new 6 puck in

I'll be using Redline's new MT85 when I change mine. So happy I don't have to mix six from them now!

Ago, like Jerry already mentioned Nissan fluid is what most people go with, just make sure if you do use something other than the Nissan fluid that its a GL4 fluid and not GL5. GL5 has a high level of sulfur in it and will hurt the brass synchros in the Z's gearbox.