Should I go full synthetic transmission oil?? I was thinking on switching synthetic on both my engine and tranny, Any input?

Manual or automatic?

It's has an automatic.

Synthetic lubricants are arguably better in almost every way. That should get me flamed.

 

I use synthetic gear lube and motor oil, and I use a synthetic blend tranny fluid. What does the 4EAT hold, something like 10 quarts? A good synthetic tranny fluid is about $7 a quart IIRC, so $70 for tranny fluid is a little spendy for me, especially since I change it once a year along with the filter(~$30). I don't flush the tranny and usually get about 5 quarts out. I just haven't seen the benefit to synthetic tranny fluid like I have with motor oil and gear lube, unless you are getting it really hot all the time. The synthetic blend (~$3 a quart)tranny fluid may be a total waste of money for all I know, I haven't noticed any difference. I am going to continue using it for the rest of the life of the car.

Well, allow me to throw a bucket of cold water on you!

 

I agree totally, Synthetic is the way forward - unless you don't intend to keep the car for a long time.

I use full synth in the engine, rear diff and power steering.

I use semi synth in the manual gear box and have silky smooth shifts. I even can get first without really stopping ( approx beween 3 to 5 km an hour).

Let's say you plan on changing the fluid fairly regularly. And you don't enter endurance races. Conventional, name brand ATF is probably fine.

 

If you change your ATF at least semi-frequently, you are doing it more often than the rest of America, rest assured.

 

If you are constantly stressing the tranny, or go for looong periods between fluid changes, I'd go with the synthetic. It's friken' expensive, though.

 

Regular fluid changes couples with a resonably-sized transmission cooler ought to extend your transmission life for thousands of miles.

I have gotten in more wars on here about this topic than you would believe.

 

I tried Redline full-synth gear oil in my gearbox for a while. It was horrible. I had to double-clutch to shift into 4th, otherwise I would grind.

 

My theory is that synth is too slick to allow proper synchronization of the gears in Subaru trannies.

 

It's possible that it's too hot here in FL for me to use synth, I dunno. But for my situation, I have to go with dino.