I actually replaced the Mobil 1 gear oil once! It came out just a little bit darker than it went in, after 100,000 miles of service. I have NEVER replaced synthetic gear oil again. Of course, the newer Toyotas are delivered with synthetic oil throughout, making replacement IN MY OPINION unnecessary.
I would tend to agree, though I wouldn't go as far as to say unnecessary.
Very few people properly service their gear/diff oil and it simply is not a cause of breakdowns. Of course, the wear is so slow that the driver would not notice the change unless comparing it to a new vehicle.
100k change intervals should be fine.
I strongly suggest that you stick with the Toyota WS trans fluid, just to eliminate any warrantee problem with Toyota.
Big, big +1.
There are a number of aftermarket products that claim compatibility, but when I see one that claims to be WS/T-IV/Dex-III compatible, I raise an eyebrow.
When GM introduced Dex-6 on 2006 models, my trans guy researched it and was told by Mobil that the Mobil-1 synthetic Dex-3 was completely incompatible with the Dex-6 systems (and GM was replacing Dex-3 with Dex-6)
Since it was a Duramax with the Allison trans, I ended up going with the Amsoil "TransSynd" which was an Allison approved equivalent to the Allison "TorqueDrive" which was the "proper" fluid for the Allison 1000 used in the GM trucks.
Does anyone here know if the Toyota WS trans fluid is synthetic?? I think it is, but am not certain.
Most transmission fluids are primarily, if not all synthetic.
Remember, ATF is more of a hydraulic fluid and coolant than it is a lubricant.
Back in the "bad old days" whale oil was a component of ATF.
I was considering a trans flush at 50K to 60K, to be done by Toyota, but I think the 125,000 mile extended warranty I recently purchased eliminated the need for that. Does anyone have a thought about that?
Toyota considers WS to be a lifetime fluid, which is the reason for the sealed transmissions.
That said, a couple of years ago, Toyota released a statement that the WS fluid should be changed at 100k for severe service... heavy off-road use, towing, or other activities that drive elevated transmission temperatures.
50-60k would certainly be overkill, but your extended warranty won't be used anyway... there would almost certainly be no failure of your trans inside of 125k that could be prevented with a fluid change.
My wife just traded her '04 Rav with 150k on it... we've never had the trans serviced and it was rock solid. My '08 Tacoma has 136k on it, likewise. No rough shifting, no noises, no gear whine... I can't tell the difference from when I bought it in '12 with 53k on it.
Both of these transmissions use T-IV