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04 Gs300 Rear Diff Fluid

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I know this topic has probably been beaten to death but i searched the forums and on google and could not find a specific answer for this. What fluid is recommended for the rear diff? I dont have an owners manual nor do i have a service manual but this weekend is supposed to be warm so i wanted to change the diff fluid before it gets cold again. If someone could tell me what diff fluid i need it would be great. I also heard that synthetic is recommended for the rear diff but wasnt sure if that was the same thing recommended by the factory. I appreciate the help.


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I guess with over 70 views this is something not a lot of people know? If someone has answered this already somewhere else and that is why no one is posting, could you please post a link or something. i know im a noob but please if someone has this info, i wanted to replace the diff fluid today so if someone could please let me know that would be great.


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  • 1 month later...
  • 3 weeks later...

Btw for future members looking for this answer, it's synthetic 75w-90 differential oil... You could also use 80w-90 if you'd like. 2quarts should do it. I use the good stuff personally, royal purple synthetic 75w-90. Not cheap but good *BLEEP* for sure

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  • 2 weeks later...

Specs in my owners manual for 2003 GS300/430 for Differential = 1.42 quarts, Hypoid gear oil API GL-5, SAE 80W-90.

Yea thats if you choose to run Hypoid oil, which is rarely even used or recommended by Lexus. Lexus runs "Toyota Genuine Differential SYNTHETIC gear oil API GL-5, SAE 75W-90" in most of all there cars now because its unparalleled protection yet at a lighter weight, reducing warm up time, and "supposedly" increasing gas mileage, with far superior protection.

If you notice now, most of the products seen are 75W-90 (synthetic). Even know 75W and 80W differ very slightly, its the characteristics of Synthetic that are paramount when comparing and choosing.

The first number, with the W next to it (75 vs. 80) is the kinematic viscosity, like I mentioned is the "thickness" of the oil shall we say. 75W being slightly thinner than 80W, which directly correlates to the warm-up time of the oil. It's a linear relationship. The thinner the oil, the faster it can get to operating temperature. The other positive linear correlation is: the higher the kinematic viscosity, the higher the protection. But the difference in viscosity is so minute that you will not be able to find differences between the two without specialized test equipment. Again, its the properties of the Synthetic oil that are prime to the choice of which to run now..

Synthetic 75W-90.... use it. I personally like Royal purple, but thats a whole nother can of worms. and btw, yea if you do a proper diff. oil change, proper meaning getting most of what is in there out, you will use sliiiightly under 2qt.'s or should.

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