When do you do which?

What do you need for each

I have a manual 2007 350z base

I'm about to hit 60k

 

Change = flush. Drain old out. Add new.

 

The term “flush” is equated to special product to remove contaminants. It may be applicable to the cooling system. You add a flush to the cooling system, run the motor, then drain.

There is no need to use a special product to flush the transmission. Unlike the cooling system, there is no place for transmission fluid to “hide.” A simple drain will remove 95 percent of the old fluid.

 

usually for manual transmission you would change the gear oil when you replace the clutch, this depends on your driving aggressiveness. changing it sooner prolongs the life of the syncros (mesh gears).

 

Correct, however a flush is required for automatic transmissions since there is lots of places for the fluid to hide. You don't need any fancy product though, all they do is just pump a bit of ATX through it to help wash out any old stuff that will pool in your torque converter and I'm sure other places. You have a manual transmission though so there is absolutely no need for any flushing.