Use stock weight oil it's either 5wt or 7wt. you can play with oil level when you get the right plushness on the first part of the stroke by using the clickers but find out it bottoms to easy. you can raise the oil level a little at a time to stiffen the last part of the stroke. Keep good track of how much oil you put in so if you put to much you can take out the desired amount. I use a small funnel that screws into the air bleeder hole on the fork cap. You have to compress the forks with a tie down screw the funnel in place and add the desired amount of oil then release the tie down when the forks extend the vacume in the forks sucks the oil right in it works sweet. When you put stiffer springs you most liklely will need to back off the compression and crank up the rebound.