First off I am one who does not care for OEM fluids, I dislike them in fact. To me they are far from the optimum choice. They are a "price point" choice for the manufacture, and MOST of the time you GET the price point. Toyota WS comes to mind, a horrible ATF in my opinion, unless you have an external trans cooler. It just can't take the heat. It has been said in many places to be a semi-synthetic even though Toyota says it is a full synthetic. I call BSS on Toyota. I had a full load of fully burn WS at 22,000 miles in a Rav4 that has an improperly designed transmission cooling setup with it's small "hockey puck", self designated description of " fluid heater" and having NO fluid cooler" as say Toyota trucks and most all Lexus have. I now have an external cooler and a full exchange of Redline D6, thank GOD.
Let's tackle the license BSS next. No manufacture will EVER license an oil other then theirs, except Chevy with their Dex-tron rating/specs, which means you could use different brand named oil that state that spec and it then is clear sailing for the chevy dealer in every way. I am a foreign car guy, so I maybe wrong here. As for foreign car manufactures they say use our fluid ONLY. Most all are Dex-tron based too. As if they have some kind of "special"additive for their transmission. When in turn when you compare their fluid to say a Amsoil Signature Series or a Redline D6, the OEM fluid is really a sub-standard fluid with a mediocre base stock and mediocre add-pack. IE "price point" without added robustness built in for rough service swings.
Before going to examples we need to address car forum and oil forum DOGMA. The class of people that thinks the manufacture is right in every way and choice they offer you, the consumer. You will get the comments like" so you know better then the manufacture's engineers" or " do you think the manufacture would use [censored] oil in their products and then in turn have warranty issues that would affect THEM later". And then we have the "I ONLY follow the manufactures manual" or "look in the manual and only go by that". If we did that we would not break-in a motor in a truly proper way or break-in brakes in a truly proper way as we see has been altered by experts and after market companies. They don't have a flock of attorneys on staff to crush "the proper way to do things", out of following actuarial tables that alters how you, the consumer as asked to do things in the car manufacture's manual. No, following what the manufacture says to do is not always right for YOU, many times only them or just mediocrity.
I myself always want to go with a group 4 or group 5 ATF, CVT, and a gear oil. Period. A motor oil I will use a group 3 without hesitation. A lot of OEM oils are not chosen for rough service, therefore they can fail prematurely in that kind of application. We could use my wife's Rav4 WS as an example, WS was not designed or have the capabilities to be used in a 600hp application, where Amsoil and Redline can handle that application with ease. I have also rid Honda DW-1 from my Honda's because it is far from a great ATF in my opinion, again price point ATF.
We know Amsoil and Redline have a superior group 4 and group 5 base stocks and advanced add-packs then almost every ATF, CVT and gear oils that comes OEM then anyone but the most exotic super cars. And as far as price, moot point. The guy who makes $50,000 plus a year whines about a price difference of $25 to $50 when he gets such a better ATF for the 40,000 to 80,000 he leaves it in, which could equate to 3 to 8 years. Just don't go to dinner with the family one night.
And for all you people who worry about warranty, at least in the USA you have the Magnusen-Moss Warranty Act which lets me take a new Rav4 off the lot and dump the [censored] WS and put in Redline D6 or Amsoil and still have a full trans warranty. You would be doing Toyota a favor by putting in Amsoil or Redline and getting rid of WS. WS stands for "worst _ _ _ _".
Which do I like better? I am more of a Redline guy. If I am going to spend the money, I want to use a group 5. Even after I always went this route for the most part, I am more inclined to go with a ATF that is a group 5. At work I was fighting a rotary screw air compressor varnishing issue with the best group 4 (PAO) oil from different manufactures, they all failed. I went with a group 5 (POE) and my varnishing problems are gone!!!!
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