Topic: Fork oil or ATF?

[nevernoluck]

What's your preference and why?

[jamesbekman]

Fork oil.  Because ATF was suggested to be used as it had better anti foaming properties that new fork oil meets and surpasses.  Also for recommended viscosity.

[tlbranth]

Newer Hondas call for ATF. Randack says fork oils are expensive and unnecessary. One of the most revered contributors on the Saunders Goldwing site recommends ATF. So now I'm using ATF on all my bikes.

[fendersrule]

Even older Hondas call for ATF per the manuals, like CB750s.

The truth is that ATF works great for forks. The only downside is that it is of lighter weight and will promote softer (but not overly spongey) dampering.

ATF will work great, is readily available, and is cheap. But if you want something a bit firmer, go with fork oil.

[LesterPiglet]

Dampering is a good word.

[Djfob]

Honda atf since I have some laying around for my cars. Also when I asked the same question fork oil was only recomended if I was intending to ride on track.

[74750k4]

I wonder if my leak is exacerbated by my use of ATF???

[crazypj]

I've been using full synthetic multigrade motor oil with great success.
10w/40 works for me. 
ATF is recommended because the specification is controlled so the 'same' oil is available worldwide

[Dave Voss]

I wonder if my leak is exacerbated by my use of ATF???

This is the biggest complaint that I hear about using ATF in forks, most folks like the feel and the price point, but it seems to leak sooner than fork oil does.  Fork oil clings better the the fork legs, and in doing so it keeps the seals wet, which I believe helps prolong their life.

[Muckinfuss]

ATF by design is packed with a long list of modifiers...all good.  I'd be surprised if ATF was the cause of failed seals in your forks.  People who don't change their auto transmission fluid, and there are many, don't see fluid all over the floor of their garage from failed seals, (other than loose pans!).  Some of the modifiers are specifically aimed at keeping the 100 or so delicate o-rings and other seals that operate under pressure and heat pliant and operating for many many years at a stretch.  Long winded, I know, but understand the science and then make your decision. 

BTW, ....the 'weight' equivalent of ATF is usually spec'd around 7 1/2.

[Dave Voss]

I suppose the point that I would make is that ATF was designed for use in automatic transmissions, and Fork Oil was designed for use in forks, each with that specific application in mind.  Cross applications certainly can work, and I know some of those applications have huge fan bases, but as long as a specific application fluid is affordable and widely available, it's probably the sensible choice for most folks.

On a similar note, many automobiles with power steering that use ATF in lieu of Power Steering Fluid also tend to leak more often.  I once bought a used car that had a power steering system leak, after draining out the ATF and refilling with Power Steering Fluid (the yellow-ish fluid, not the red fluid) the leak fixed itself.

[jamesbekman]

Yea fork oil has a higher viscosity plain and simple.

I dont quite get the motorcycle fork tube to a cars automotive transmission comparison. 

[ofreen]

Stiction is always an issue in these old forks, especially considering most of them are showing some wear by now. ATF works, but I found a good fork oil leads to less stiction. The difference in small bump and high speed compliance with fork oil over ATF was always apparent to me. I use PJ1 these days, but there are other good ones.

[Bankerdanny]

As a relatively heavy guy (225 lbs), I prefer a heavier weight oil, particularly in my Goldwing, which is heavy itself AND has a fairing, but I also liked how it worked on my stock CB550.

The Honda ATF recomendation was based on testing by small japanese men on naked bikes.

[RFogelsong]

To add to the conversation, I've heard that ATF swells seals.  I've had god luck with it saving a seal in a petcock by swelling it to, so here's the question:

If you had fork seals that were on their way out, would running ATF inside the forks be of any benefit in trying to preserve those?  I ask because I'm not really sure how much ATF would get up to the seals because of it's lower stiction when compared to fork oil.  On that note, would a better application of ATF be to wet the tops of the seals if your goal was saving old seals with minor leakage.

Having said that, I've got fork oil in my bike and it does what it says on the tin, so if it ain't broke...

[garyS-NJ]

I read a lot and ended up making my own blend of ATF, fork oil, and hydraulic oil (with a sealant in it).  seems to work good.

[Xnavylfr]

Recommended oil straight from HAYNES manual

SAE 10W-30   CASTROL TQF    http://www.tds.castrol.com.au/pdf/9772_TQF_111805_2008_03.pdf

TRANSMISSION FLUID!!

Xnavylfr(CHUCK)

[crazypj]

That's interesting, I didn't know it existed but I'll look for it next time I'm in autoparts store

[phil71]

Another property unique to ATF is it's 'growth'. If you put a pan full of ATF out in the sun, it will spill over the rim pretty quickly. I can't picture how that is good for consistent rates of damping.

[nevernoluck]

Recommended oil straight from HAYNES manual

SAE 10W-30   CASTROL TQF    http://www.tds.castrol.com.au/pdf/9772_TQF_111805_2008_03.pdf

TRANSMISSION FLUID!!

Xnavylfr(CHUCK)

yep I've gut a fancy book for it too, doesn't mean it's the only stuff that works

[surveywaters]

Fork oil for me all the way. It's adjustable to your riding style, treats old forks better and is relatively inexpensive. If ones main reason for running ATF is that it can swell old seals to make them last, they should just accept whatever their mechanic puts in the forks at rebuild time.

[azuredesign]

Fork oil for me all the way.

+1, from my reading the weight of ATF is variable and inconsistent. Changing fork oil even at 200cc a leg is less than 5 bucks with real fork oil. Can’t we find something else to economize with, like coolant?