Oil/ATF mix, or fork oil?

[k.graham]

Hey everyone!

im going to tackle my fork seals on my '79 GS 550 today hopefully. I read through the service manual to check the specs on what I'll need. Suzuki manual (thanks to basscliff!) calls for a mixture of oil and ATF. I'm wondering if that's just the way they did things back in '79 before fork specific oil was widely available? Is it better to stay with what the service manual says, or go with actual fork oil? I researched this a bit and everyone seemed to say that you should use fork oil in your forks and not mess around with anything else. To the best of my knowledge, those threads were about people trying to save a few bucks and going off spec. What about in the case where the manual actually suggests the mixture? Will either work? If so, which is the better choice?

thanks in advance for your help!

[Guest]

Fork oil. 10W or 15W.

[JJ]

I use 15W fork oil. But, I weigh 235#.

[bwringer]

Yep, fork oil.

I use 10W, and I'm an enormous hairy galoot who rides too fast.

I highly and strongly recommend upgrading the fork springs if you haven't done so already. Our friend Rich from Sonic Springs sells righteously sproingitudinous straight-rate springs for a pittance. Here's his spring rate calculator:

http://sonicsprings.com/catalog/calculate_spring_rate.php

[Agemax]

fork oil. as you so rightly state, those manuals were published in the 70's before "proper" fork oil became widely available.

[Gorminrider]

Contrarian that I am, need say that Honda was telling bike owners to mix atf and multigrade motor oil up to 1981 at least.... As to WHY, I've never heard a satisfactory explanation and, I've used the mix without any bad result I can find. But I'm not stressing anything very much. The mixture equates to about 7-12 depending on how you describe viscosity of ATF and what effect a multigrade would experience in forks.... ATF is obviously as seal friendly and antifoaming.

That said, I like fork oil too if only to save thinking about it. And, later manuals for my 82 650 say "#15" which I assume is 15 fork oil. You could look ahead at newer manuals for your bike or similar and decide around that.
..... It might be interesting to compare the MSDS of ATF and "forkoil" to try to figure out what the differences are.

were about people trying to save a few buck

not exactly. I just Hate being sold generic products at higher prices. I want to see where the value is, beyond putting stuff in smaller bottles...

[k.graham]

Thanks everyone! That clears it up for me perfectly. I have some 10w fork oil handy, so I'll stick with that. I also like that it's one less thing to measure out, so if anything less margin for error and ultimately less hassle!

[Nessism]

ATF varies in viscosity so it's hard to judge what you are going to get. 10W fork oil is what I use.