Yes, it is recommended to use OEM for rear diff and transfer case, Amsoil does offer motor oil and more that protect engines. I switched from OEM to Amsoil 6 years ago and I have no problem what so ever. I took it to my regular mechanic here in Vegas to change out my valve springs, retainers and cams, he said he didn't see an engine block so clean. He said 6 years ago when he recommended Amsoil to me, it will clean and protect your engine. But to answer your question. I use the severe gear for my 4x4's. For more info click below, this will give you all the information and type of fluids recommended by Amsoil for an Evo 9. Hope this help.

http://www.amsoil.com/mygarage/PRNoM...px?unitid=9403

 

Lol... It's actually worth it. When you care about your Evo, you want the best!! I'm not saying OEM or any other brand isn't. But I wanted oil and fluids that can clean and protect my engine for longevity. I did all the research and found Amsoil, in MY OPINION does what I want for my Evo.. Everyone has different opinions about oils and fluids on what can they do for your engine. But at the end of the day, everyone want that #1 common thing about there Evo, to keep it clean and protect that engine as long as you can. Ohh and to be quick and fast, of course... lol

 

If you have the cash, the stuff works just fine. I'm just teasing. In a lot of instances, it's kinda overkill. But like you said: it's just opinion.
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used to run amsoil everything, switched to red line and I'm seeing better wear patterns.

also, amsoil's gear oils don't match up to the additive packs in the diaqueen stuff - red line's does:

https://www.evolutionm.net/forums/ev...iscussion.html

I run amsoil in my pedestrian cars for extended OCIs, amsoil has more TBNs than red line in general. but red line for the cars that get raced, for sure.

 

I'm a believer in Amsoil keeping engines clean. I had a Civic with a swapped motor and over 230k miles on it and Amsoil kept the internals clean as a whistle. This was with OCIs at twice a year because I was lazy. Sold the car last year and it's still running strong.

My drivetrain is due for a flush. Because of this comment I'm going to give Redline a shot this time around.

 

 

Diaqueen LSD oil is always the way to go. Amsoil don't offer LSD oil for an Evo 9, they recommend to go OEM, as stated here http://www.amsoil.com/mygarage/PRNoM...px?unitid=9403 Redline has a great line of products and has the proof to back it up. Personal preference to me, I live in Vegas, being the weather is hot. Amsoil cleans and protect the engine like you said. And they also have that great line of products and the proof to back it up. All brands of oil has its pros and cons. Bottom line, everyone want the same thing, clean and protect that engine for longevity drives.

http://bestvehicleprotection.com

 

see the link I included. I set out to find what makes diaqueen so special... the answer - nothing. I did VOAs on some of the more popular gear oils, including a special request 40C above normal operating temp.

amsoil shouldn't recommend a gear oil, their additive packs don't match (boron and phosphorous are the main ones for diaqueen) - and actually has less than diaqueen. red line's does and has more than diaqueen. that leaves the film strength, which is top notch in an ester-based oil like red line.

this diaqueen only mindset has been extremely pervasive in the evo community for over a decade. I'm hoping that changes over time with those results

 

I always use the Mobil 1 filters. M-104, 108, and 110 I believe all work.

 

This reminds me of how BMW Band-Aid fixed the E46 M3s plagued with bearing problems by forcing owners to use an expensive spec'd motor oil made by Castrol. If an M3 came in with bearing problems and was found to be using any other oil, the warranty would be void. Those guys were so hung up on that oil that anyone who even mentioned another brand was instantly flamed on. I applaud you on your effort for testing the Redline fluids. If there is another viable option to Diaqueen, I'm all for it.