aaronk

New Toyota owner here so please forgive me for all the newbie questions...

I've read that switching to synthetic oil on a high mileage truck could cause some leakage, but does the same hold true for switching to synthetic gear oil in your diffs, transfer case, and tranny?

I've got a 1994 4WD M/T Pickup that's got 178K. I'm sticking to regular oil for the engine, but would like to use synthetic in the above mentioned components. Do I have anything to worry about in doing so? I have no idea what the previous owner was using, or if he even changed those fluids at all...

Any words of warning?

OSU4Runner

I switched to synthetic at 60,000 miles when I got my truck, haven't had any problems during the 20,000 I've put on it.

toy_tek

No. I changed to Amsoil around 125k. No leaks at 145k.

NCGuy68

I've been running Amsoil gear lubes in high milage vehicles for years. Never had a leak that was directly associated with synthetics.

aaronk

Thanks for all the quick replies!

Sounds like the leaking issue is just if switching to synthetic engine oil then? And even then it seems like a hit or miss issue from what I've read.

HAVOC

I've heard that changing to synthetic wiil make your engine leak because it's "thinner", and not meaning viscosity. Where do people come up with this stuff?

OSU4Runner

I've heard that it gets into the seals and tighter spots where conventional oil doesn't lubricate causing the engine to leak or seap a little. I've never had a problem.

mjwalfredo

Just more hearsay but I hear it's the detergent qualities of synthetic oil that clean the deposits off the seals and cause them to leak when they are already bad. Of course I switched to Mobile 1 with 198k mi on my 3.4 and have had no leaks. Actually, my cylinder head cover gasket actually seems to be leaking less than it used to. I wouldn't worry about switching to synthetic gear oil one bit.

Gt4r97

No, switch mine @113!

Gt4r97

Maybe if you have small seepage, synthetic will flow freely that a dino. Not sure though.

mkgarrison5

you will be fine and you can use any syn lube you want too. find one on sale and use it.