twiztids4

i am going to change all the fluids in my 2000 manual s4. i have searched for days on what to put in my transmission. i have always had good luck with the royal purple so i will be using that in everything BUT the transmission. i have read that the gl5 rating on it kills the copper synchros. i am really looking for a solid answer on what fluid to use. i want one that will get most mpg and best shifts. i have heard redline mt90, redline mtl, shockproof , etc. i hear motul doesnt shift good in cold climates. i live in ny. temp ranges from 0 degrees to 100 degrees F. i am really just looking for a straight answer with less opinions and more actual experiences. what is the all time best fluid for these transmissions. if it happens to be the stock i will gladly replace it with that. i have been running in circle for days trying to pick the perfect fluid for this. thanks in advance...

twiztids4

Amsoil also looks good on paper but I read if the synthetic is too slippery it can also harm the synchros...

P0234

Can't comment much on the fluid except for the PO put Amsoil in my S4 about 25k miles ago and it shifts amazingly well for a car with 100k.

One thing to note, be SUPER careful on which plugs you pull. There are a lot of things that look like drain/fill plugs but a few of them spell disaster if removed.

Peter Badore

I like the VW/Audi OEM fluid and there has been a price reduction recently.

Ritz

I've always used Redline MT90 in my B5's and C5's. It has performed well in NY/CT winters, is relatively easy to get, and doesn't cost a fortune.

Best,

shawnoc2003

Ditto on the Redline. I put it in all the diffs and transmission. Everything has been great for the last 30000 miles. For reference, in the summer I get ~30mpg on the highway at 70mph.

For what its worth, I just put royal purle in my 2006 Denali's diffs and transfer case and haven't noticed any improvment in mileage.