Toyota ATF WS - synth? Is it any good?

rcy

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I just picked up a 2006 Lexus RX400h. Toyota ATF WS is spec'd for the CVT and the rear diff (the regular RX still uses gear oil in the rear diff - on the 400h, the rear wheels are driven by an electric motor). I found this regarding the fluid. Does anyone know if this stuff is synthetic and is it a decent fluid? The vehicle has 115000 KM on it, the diff takes 2 litres, and when I changed it, it still looked pretty good and smelled OK. Mind you, I don't think the rear diff gets a whole lot of use in this vehicle. It's mostly FWD with the rear only kicking in on acceleration or slippage.
 
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I've seen a few posts that mention WS fluid has not held up well, at least on observation. I thought WS was syn, but I'm not sure now. I see the new Amsoil equivalent to WS ( called ATL ) has a vis of 6.0 at 100C, whereas their equivalent to T-IV ( called ATF ) has a vis of 7.6 at 100C, so I'm not sure if the ATL would be compatible with your tranny. I see nothing listed for your rig on their lookup guide.
 
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 Originally Posted By: benjamming
I've seen it mentioned as well but never which tests exactly it did not fare well.
Toyota fluid over all does not seem to hold up well.(T-IV) Now their coolant (red) is another story,very good stuff.
 
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 Originally Posted By: rcy
I found this regarding the fluid.
Is this official Toyota publication? If so, this would confirm that the difference is only viscosity and that toyota owners driving in hot climate or towing could use regular Synthetic ATFs rather than the low viscosity ones.
 
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Its direct from the factory service manual. I would think that a full synthetic, even if thicker at normal temp, should have no problem meeting the cold flow requirement.
 

rcy

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I'm supposed to use ATF WS in the rear diff and the CVT. As mentioned the rear diff is actually an electric motor driving the rear wheels. The CVT is...well...a CVT. The car is out of warranty (except for the hybrid components, good for 8 years or 160000 KM) but the amount of technology in the hybrid is amazing and likely expensive to repair. Just to be on the safe side, I think I'll stick with the ATF WS and change it every 24000km. I have already changed the rear diff with fresh ATF WS. It didn't appear to me that the drain or fill bolts had ever been removed. The fluid was still more red than brown and it smelled OK as well. This was after 115000 KM. However, the rear diff only gets used occasionally (on start up and upon slippage). A better test will be when I change the CVT fluid and see how it looks/smells.
 
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 Originally Posted By: benjamming
hold up well per what test(s)?
In my (opinion) from what I see myself,and read on the Lexus boards.The Toyota trans.fluid is not one of the better fluids out their.
 
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 Originally Posted By: benjamming
I've seen it mentioned as well but never which tests exactly it did not fare well.
The info is in the SAE paper.
 
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