I am about to do my 30,000 mile tune up in two weeks time and was wondering if the stock LSD on the IS300 required any additive for the diff? I bought Valvoline Durablend (Synthetic Blend) 80W-90 Gear Oil today and wanted to know if that is all that is needed? Thanks.

 

Welcome !

If you check your owners manual to confirm,

The gear oil should exceed API GL-5 specifications and

Meet the service fill requirements for limited slip differentials.

 

You shouldn't need any additives with these synthetic differential fluids.

In addition, I believe your stock fluid might be an 85W90. My RX calls for an 85W90, but I have used a 75W90 Royal Purple MaxGear differential fluid (without any additives) in my RX300 without issue.

Thus, that 80W90 should be more than sufficient and no additives.

 

No special additives are needed for the OEM Torsen type rear ends as this design doesn't use clutch packs like some others. If you have fitted the after market TRD LSD, that unit uses the clutch pack design and would benefit from the friction modifier additives.

AFAIK, Lexus did not fit any IS300 from the factory with the TRD unit though.