Scotty, et al,
It says on the label that this fluid is compatible with Toyota WS- world standard transmissions. Would this be acceptable to use this in my 2007 Lexus ES350 with 164k miles on it's next fluid change? Will it interfere with the old WS fluid that remains in the transmission if I perform a drain and fill? You've mentioned before that synthetic fluid is more stable and temperature tolerant.
My basic question is: Is it good or bad or makes no difference to mix synthetic transmission fluid with non- synthetic fluid?
If it is compatible there should be no issue.
Here is the best explanation I've found about conventional vs synthetic oil;
If the label says it's compatible then you should be OK. I don't know what specific brand of ATF was originally put in my car or SUV but I drained out what was in the pan and refilled with the full synthetic maxlife multi-vehicle valvoline ATF and haven't had any issues.
There is no issue typically mixing synthetic, and non synthetic transmission fluids. I have done with with numerous older cars with good results. If it were me, I would spring for the more expensive amsoil fuel efficient for your scenrario. That stuff has worked terrific for me in my GX470 and my 2013 prius.
I did use valvoline max life atf in my 98 f-150, and it did okay, but then I switched out half with amsoil, and it improved the shifting quite a bit.
what is "synthetic" oil? It's the same as conventional oil, just more refined (allegedly). That means everything that's in synthetic oil is already in conventional oil, right.
