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Dec 13, 2002
North Carolina
I have been reading on here that these two oils are the same just different labels put on the bottles.

My question then is about the wet clutch properties of the AMF vs AMO. Is the AMO able to be used in a motorcycle with wet clutches?

So if that is the case then either could be used for a bike?

Now, how does that effect the use of these two oils for regular automotive use?

Why isn't all the oils wet clutch compatible if it isn't needed?

Just was wondering and wanting to learn more on this.

As far as I know, these are still the same formulation, and both are "JASO MA" rated for use in wet clutches - that's the highest rating you can achieve. Of note,the S2000, 20w-50 racing oil is JASO MB rated, for use in wet clutches. Many of the folks who race motorcycles with Amsoil use the better S2000 stuff, either the 20w-50, or even their 0w-30 to gain more Hp.

Amsoil does not use any borate friction modifier in their MC oils. However, this is a marketing decision as much as anything else. The original Amsoil 10w-40/20w-50 have been used in wet clutch bikes for over 25 years without causing any problems. The type of oil soluble FM's that Amsoil has always used don't mess up wet clutches, period. I suspect this is because they don't chemically interact with organic clutch plate materials. Solid based FM's like Teflon or MoS2 do cause problems, because they mechanically/physically decrease the surface roughness of the clutch plates, which reduces the Cf of these surfaces. (Quite honestly, just thought of that theory as I was writing this, but it makes sense.)

Friction modifiers are added to xw-20 and xw-30 gas engine oils to help them pass the Sequence IV, fuel efficiency test. This test is required for the "SL" and "GF-3", gas engine specifications. A FM will typically increase fuel efficiency by 1%-2%, although it is debatable how long this effect lasts. These oils are only required to show fuel savings out to 96 hours with an engine used on a test stand, which equates to approx 4000 miles of use on the road ....The # of fuel savings required after 96 hours is significantly less than what is required after 16 hours of testing - about 40% less, as I recall.


[ February 15, 2004, 07:39 AM: Message edited by: rugerman1 ]

That brings me up to speed in that area of oil. I just need to have things explained in laymans terms so to speak to get the full grasp.

Thanks again.

I work with engineers and physicists every day, so often I end up talking over peoples heads and confusing them without trying, but using a bunch of technical mumbo jumbo.

If I post something that is not clear, please let me know and I'll try to make it more understandable. In a previous life, I was actually a graduate teaching assistant in the materials science dept at Georgia Tech.
I'd like to retire from NASA and teach HS physics in 5-6 years, if things work out ....

So I'm really practicing my future lesson plans on you guys as much as anything else


Originally posted by Rat407:

That brings me up to speed in that area of oil. I just need to have things explained in laymans terms so to speak to get the full grasp.

Thanks again.

First post here, hi everyone.

Anyway, I own now, and have owned several sportbikes in the past. I've never used a motorcycle specific oil, always automotive oil. At the moment, I'm using Castrol TWS 10w-60 Racing oil. Many tell me that the friction modifiers in auto oil will cause a wet clutch to slip. I've NEVER had a problem with it. My Hayabusa's clutch isn't slipping, nor is my GSXR600.
However, in drag racing applications, which I don't frequently do, there may be a difference in clutch bite, or clutch life. I've never really heard anything on that. Drag racing is very hard on the clutch. I'm not a drag racer, so I don't know.
Pesonally, I believe that friction modifiers are a good thing for the engine, and I'd rather fully protect the engine that worry about a possibility that the clutch may slip.

Hope this helps. This is a great board. I hope to learn and share all the info that I can.

Yeah, we all need something to occupy ourselves with. I'll take fishing and watching SOME sports along with my vehicle tinkering.
Welcome TECH.

Yes this is a great board, and I have learned a ton from all the experience on here. Thanks for the post.

As quoted once but not sure who it was "knowledge is power" I like to think my grey matter is still absorbant and want to learn what I can. Not to mention I really enjoy all that this board has to offer. I'm not one for other interests, don't hunt, fish, golf, or watch sports on tv, but like to tinker with my vehicles.
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