I've put over 40,000 on it. I'll most liekly change the fluid again soon just for the heck of it. I'm just trying to keep up with everything else on the car. Check out www.redlineoil.com for viscosity info/ratings. It doesn't get too cold here in NC, so I wasn't as worried about the viscosity at colder temps (32 degress and less) becuse it just doesn't stay cold for long stretches here as it does up north.