OS Giken Differential Gear Oil Fluid – 80W-250 Grannas Racing

Questions regarding our LSD and what fluid to use has come up quite frequent in the past year. We just want to provide users with information to help explain why OS-250R is important and why our LSD’s have a select few of approved fluids.

OS-250R
OS011-KA1

Most diffs take 2 quarts

Our differential is a Negative Preload Type LSD and thus our differential starts out with little to no locking until power aggressively applied. Because of this design it is critical that the right type of gear oil is used to ensure proper break-in and long term performance. If any incompatible oil or fluid mix (gear oil + LSD friction modifier) is used, the differential may not lock properly or may chatter and lock inconsistently.

OS GIKEN OS-250R gear fluid is a specially formulated synthetic gear oil that contains the proper amount of gear oil and limited slip additive for LSD protection and reliable locking performance for our RWD applications (currently, OS-250R is not recommended in transaxle applications). With that being said, we have had success using a select few non-OS fluids in regards to protection. Please see our current list below:

• Motul Gear Competition FF 75W140 – (FWD Transaxle, AWD, and RWD Applications)
• Motul 300 75W90 N/S – (FWD Transaxle, RWD)
• Swepco 210 – (Old Porsche 915/930 Gearbox Applications)
• Motocraft Synthetic Gear Oil 75W140 – (FWD, Transaxle Applications)

As we are constantly testing units with different fluids and will update this list as more come along. These are the select few over the years that have proven to work well in their given application.

If you have any questions, or have any particular oil you would like us to test, please feel free to contact us at your
earliest convenience!