sjc2467

I recently acquired a '93 SC400 with only 23k miles. It doesn't really need anything, but other than the oil (just changed, Amsoil HDD 5w-30) and transmission fluid (changed shortly before I got it, by the dealer), most of the fluids are probably 20 years old. I was thinking about changing out the PS fluid and fan fluid (both Dex II ATF, I believe) with some Amsoil Torque Drive ATF (supposedly one of the best Dex III compatible fluids there is). Even if it's not really necessary, the synthetic fluid will probably help mileage a bit (particularly on cold starts, because it doesn't thicken like conventional fluids), and as long as it's compatible (I think it is) it certainly shouldn't hurt anything. I have almost a gallon, from another vehicle, which I'm guessing will be enough for both systems.

Any reason not to do it?

I assume the best method, for both systems, is to siphon out the reservoirs, refill, run it a bit, then repeat (2-3 more times)? Is there a better method?

I may also eventually change the transmission fluid to Amsoil Multi-Vehicle ATF, which should be compatible with the Toyota fluid. I think the dealer only changed what was in the pan, and even with such low mileage, I'm sure new synthetic fluid is a lot better than the 20 year old fluid it has. Any comments on this?

I'll probably flush the brake fluid sometime soon, as well, but it actually looks pretty clear, so I'm guessing that was done recently (the previous owner rarely drove it, but had it serviced every year by the dealer, telling them to do "anything that it needs").

Anything else I can/should do?

Thanks, in advance!

edit: forgot one thing. Rear differential: change it or leave it alone? If I change it, is 75W-90 or 80W-90 recommended? I don't see any reason not to use 75W-90, and less thickening when cold is typically a good thing, so I think that's the best bet. Again, I'll probably go with Amsoil. I have no particular brand loyalty, but I've heard great things about virtually all of their fluids, and I have a "preferred customer" account, so I get wholesale pricing.

sjc2467

I just took a look at a few things and noticed that both the PS fluid and fan fluid are a light yellow color. I'm used to ATF being red, but I think I've heard of some OEM fluids being yellow. Is this the normal OEM/dealer fluid? (I just want to make sure some "inexperienced" tech didn't put PS fluid in there, or something--normally I wouldn't worry, but according to the dealer maintenance records, they often used 5w-20 oil, which certainly isn't the right type for this vehicle.)

Any ideas on whether it would benefit from changing to synthetic fluids? I'm guessing the OEM stuff is probably pretty good, but I doubt it's as good as a premium modern synthetic... right?