Originally Posted By: ringmaster
Is there an ATF with WS-compatible specs that is higher quality than the basic Toyota WS and might provided improved shift feel? Amsoil? Redline? Motul? Mobil 1?
"Shift feel" from the standpoint of the ATF alone has in simplest terms two components:
Visometrics - the "thickness/flowability" of the oil at various temperatures
Friction Characteristics - how the base and additives work with the various friction materials in a given transmission under load, unload, and speed.
Assuming the manufacturer knows what he wants, the base "shift feel" should be a new transmission freshly filled with the OEM fluid.
Unless there is some problem with the transmission fluid in the vehicle, if you change the "shift feel" with a fluid change, you’ve changed one or both of the components and you need to know what changed and what it’s doing. Slippage in particular can cause early transmission failure.
Having said that, Red Line recommends their D6 ATF for transmissions calling for Toyota WS. I have some experience with it, and with the D4, and am very pleased. The base stock is stable, it has exceptional low temperature characteristics, and to this point shift quality seems top notch.
The downside is price - about $12 a quart. That puts it in the same price range as the Amsoil Fuel-Efficient ATF and above Motul and Mobil 1, another ATF I have extensive experience with. I’d scratch the Mobil 1 myself - it is not in the same league. Just looking at the published visometric specifications, the Red Line and Amsoil seem to track except for the Brookfield viscosity at -40c, where the Red Line is superior.