A variance of 5 mm in oil level height is O.K. In general, a lower oil level, ie. 50 mm, will make the fork more responsive or liveler for lighter weight riders.
A higher oil level, ie. 40 mm, will make the fork feel more responsive and is better for heavier riders.
When the oil level is changed the air preassure will also need to be adjusted due to the change in volume area. Less oil means there is a larger chamber air chamber, and higher oil level means there is a smaller air volume.
Approved Replacement Oils
Marzocchi stats: “Marzocchi oil item 52.5 or Finish Line Shock Oil are the only Marzocchi approved shock oils. Using other mountain bike suspension fork oils or motorcycle fork oil is not recommended and will void the warranty.”
In real you can use any other mountain bike suspension fork oils or motorcycle fork oil.
But never use car or motorcycle motor oil because it contains additives that will damage the seals and O-rings causing seal failure and possible damage to the fork.
Make sure to use the specified oil weight when replacing the stock oil. Marzocchi uses different weights with different fork models. See oil weight chart and correspondending fork models in the manual to orof. setup your fork.
In general, a lighter weight fork oil will flow through the valving faster delivering a livelier, more responsive feel while offering less shock damping. This set up could be better for lighter weight riders.
Conversely, a heavier weight oil will flow through the valving slower, offering greater shock damping. This set-up could be better for heavier weight riders. With the use of the adjusters an the XC500, XC600 & XCR forks changing from one setting to the next is similiar to changing to different weight of oils.
Dear reader: If you have some advanced tipps about tuning, oil sorts etc. which might be placed here –> please drop me a mail. THANKS!