Excellent information. Seems like the Magnesium additive really stands out in the Honda OEM fluid, why did they chose that specific additive over others?
Anyone know the reasons, seems to me like it is due to the unique design of the Honda automatic unit. They do have clutch packs like a traditional manual right?
So maybe helps limits dissolution of the friction material from just sitting in the fluid?
I also have another question, does anyone have a fresh fluid analysis of the old Honda Z-1 fluid?
I've never seen that but looked everywhere!
Whole lot of Honda ATF Discssion there, and I will offer my opinion here (Its also over there).
Back during the early 2000's Honda was moving more upmarket with their cars. They needed 'smoother' shifting transmissions in order for people to accept them as more luxury. According to Mola, the Zinc that is in the Z1/DW1 formulations acts as a friction modifier.
Looking at the design of some of the Honda transmissions over the years and looking at how they shift, there are a number of gearchanges where you will have 2 sets of clutches on the same shaft that need to engage and disengage at the same time or you will bind up the transmission and it will be jerky. If they don't switch fast enough, the shift will flare, also not good. If you have a fluid that lets the plates slip a little more, you smooth out that gearchange. No more jerks, happier customers. This is the advent of Z1 in the early 2000's. Right around the time Honda started having transmission problems.
Z1, had an iffy base oil that sheared quickly, DW1 arrived with an improved base and much the same additive package. This was mid-2000's. Several transmissions were also redesigned (06 and up Accords for one).
Fast forward to now and we have several manufacturers bottling 'specific' oils (Idemitsu/AISIN) and multi-use oils that are 'suitable for' replacing OEM DW1 (Maxlife/Etc.). The additives aren't the same, but the question becomes, do they need to be?
If we assume that the Zinc is there for shift feel, then can other manufacturers do it without? In my opinion, probably. (In my experience with Idemitsu H+, my cars shift fine, is it the same as DW1? No clue, I've changed it gradually over many miles, there's no way to A/B compare)
So, all the above is my opinion, here's me doubling down on that statement(the opinion part):
You will likely not hurt your specced for DW1 transmission with any of the aftermarket fluids 'designed' or 'recommended for'. Keep the fluid changed and clean and you are doing what you need to. The only downside is that the transmission might not shift exactly the same as DW1, or maybe it will depending on who designed the fluid. Are harsher shifts 'bad'? I know I've always heard that a firm shift is easier on the transmission than a soft/squishy one.
Take that for what you've paid for it, but I've been watching the DW1 discussion for quite some time now, have sent off and received emails from several companies on the subject, and thought about it more than any sane person probably should have.
And as for what to call the transmission? Honda calls it an automatic. Other people call it an automated manual. I suppose whatever floats your boat. The gearchanges are performed with clutch packs, no bands, no suns, no planetaries....so I'm not sure what that makes it. I'll just stick with automatic.