Dexron ATF is roughly equal to 7W Oil for the Forks...

[sgtslag]

I just posted on another forum regarding the use of ATF (Dexron III/IV, currently around $3/quart, in my area) in the front forks, in place of expensive Fork Oil (currently around $15/quart, in my area).  Someone chimed in that ATF is roughly equivalent to 7W Fork Oil.  Thought I would spread the wealth around, in case anyone was interested in this somewhat obscure bit of information.

My Voyager spec's state to use "10W-20 Fork Oil" in it (have not found a multi-viscosity Fork Oil yet...  suspect they meant that as a range of straight weight oils to choose from), so I went with 15W Fork Oil, and it is too stiff for my tastes.  I planned on trying 10W in the Spring, or possibly even 5W.  With Dexron ATF being roughly 7W, I plan on using that, and saving myself around $9 on the fork oil change.

How Dexron ATF, specified by Honda for use in forks, compared to Fork Oils, had been a mystery to me for quite a while.  When I researched what was so special about Fork Oils, as opposed to engine oils, I discovered they are super-refined, super stable under a wide temperature range; Dexron ATF shares similar qualities in stability, but it is mass produced, at a fraction of the cost -- but it only comes in one viscosity, which, until now, was a mystery.  Cheers!

[TOOLS1]

I wonder if Type F, or Mercon would be different weights?
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[sgtslag]

Wondered the same thing myself.

Ford Type F Viscosity: 43 cSt @40°C.  (13W?)

Dexron III Viscosity:  60.0 cSt @ 40 C.  (22W?  Not 7W!)

Bel Ray High Performance Fork Oil 7W, actual Viscosity:  32 cSt @ 40 °C.

Bel Ray High Performance Fork Oil 10W, actual Viscosity:  32 cSt @ 40 °C.

Bel Ray High Performance Fork Oil 15W, actual Viscosity:  52 cSt @ 40 °C.

Bel Ray High Performance Fork Oil 20W, actual Viscosity:  52 cSt @ 40 °C.

Bel Ray High Performance Fork Oil 30W, actual Viscosity:  105 cSt @ 40 °C.


All of this information was pulled off of the Internet, by searching with Google for "Fork Oil xW MSDS", where "xW" is the oil weight, like "7W", "10W", "15W", etc.  It would seem as if the Dexron III ATF is actually closer to a 20W oil, based on what is listed above.  It also appears as though 7W and 10W are essentially the same -- snake oil difference?

Caveat Emptor:  I am not an expert, nor do I understand the centiStokes (cSt) thing, so maybe I am missing something here.  When I did my Fork Oil research in the past, I found one writer who stated that it was really hard to pin down the true viscosity factor, as one maker's 10W was another maker's 15W; this same author stated that it was hard to find consistency, and accuracy even among different fork oil from the same manufacturer...  I think I discovered the same issue as he did, with Bel Ray's products.


My head is starting to hurt.  Think I'll go lie down for a while.

[sgtslag]

Here is a helpful information page discussing the W viscosity rating, along with the centiStokes (cSt) viscosity rating:

http://www.upmpg.com/tech_articles/motoroil_viscosity/

This helped reduce my headache a little.  At least now I understand what the "W" rating on multi-viscosity oils means.  Cheers!

[shinyribs]

Wow. That was a whole lot of numbers ,letters, /'s,and info.I'll have to reread that when im well rested

[TOOLS1]

When do, you rest? Every time I open the computer your on.
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[shinyribs]

If i am on when you are on then we're on at the same time...when do you rest?        There is no rest for the wicked

[TOOLS1]

I sleep during the day. One of the benefits of being a vagabond.
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[shinyribs]

I understand that  need a lot of naps