Should this be checked while the car is running, or after the car sits for a while and the level rises???

 

The level of fluid drops when the car is running as there is fluid being circulated through the system, however when the car is not running and after it sits for a while the fluid level goes back up as fluid returns to the reservoir.

 

I figured that out already, but should you set the level when the car is running, or after it's been parked for a while and the level rises back up???

 

after the fluid rises back up. you can fill the resevoir all the way up though so that when the car is running the level sits at the maximum fill line.