Does anyone know of a website or study that compares the differences among various manufacturer's oils? I've seen many references that Harley 10-weight is not the same as someone else's 10-weight for example, but never actually seen a side-by-side conmparison. I've checked all the usual sources... Bobistheoilguy.com and various forums, but still haven't forund anything conclusive.

 

I just changed my fork fluid and used Harleys std oil. It looked and smelled just like automatic trans fluid. As far as weight, it didn't say anything on the bottle about it. Next time, I think I'll just use atf and save a few $$$.,,

 

The only differences I am aware of is the differences between gear oil & motor oil. Could this be what you are thinking of?
With fork oil I think HD uses something like Regular, Heavy and Very Heavy which I think is 5W, 10W and 15W respectively.

SAE Engine Oil vs SAE Gear Oil

10w thru mid range of 20w = 75w
Mid 20w thru mid 30w = 80w
Mid 30w thru low 40w = 85w
Low 40w thru 50w = 90w
60w up = 140w

If the oil has SAE / API on the label it would be measured to the standards of the Society of Automotive Engineers / American Petroleum Institute and could not vary brand to brand.

 

Therein lies the problem... fork oil is not SAE rated. My bike calls for Type-E fork oil, w/o any definition of what weight that equates to. You won't find a definitive answer on the Web either. The best I could surmise is that stock "E" is 5w or 7w, depending on who you believe. To further confuse things, since there doesn't seem to be a standard body that manufacturers comply to, one company's 5w could be different from somebody else's 5w. You'll find anecdotal evidence of this all over the place. A lot of people believe Screamin' Eagle fork oil to be 15w, and too heavy for street use. Well if that's true, I'd be in big trouble, because I just filled mine with 30w Bel-Ray, and it's firmer but still compliant.

 

I tried the SE medium before, took it back out after a few months.
Too stiff for my taste. The roads ain't all that good in my region.

 

Ahh, guess I worded that poorly before. I didn't mean to imply that everyone who said SE made their front end too stiff was full of it. Just the opposite in fact. I was trying to point out that if 15w were too heavy then 30w would be out of the question!

I guess I'm looking for something that doesn't exist... a table comparing different weight fork oils to their equivalent in another brand.

 

E is 5 wt
B is 10 wt
SE is 15 wt
SE heavy (racing) is 20 wt

The thicker Oils are useable IF you can limit fork flex(with a brace)
and If you ride In warmer weather.
20wt works fine for me,,because of a fork brace,,an hot weather.
Prolly gonna go thinner now that Its cooler.

 

Mine was actually not that bad for the average ride and I can understand why some do well with it.
But it exagerated the little imperfections in the roads and I have a curb at the end of my driveway that reminded me every time that I had heavier oil in my forks.

 

Interesting. What is the source of this info?

 

Lucky
You might find some info on this link:
http://www.amsoil.com/storefront/stm.aspx



I'll take a wild guess here that some fork oil manufactures don't give the weight in the official "W" format because it requires the expense of testing, certification and probably fees too. Some like Amsoil use #10 alluding to 10w and it probably is but just not certified.

I did not look at the other fork oils Amsoil has but they likely will have a table of similar weight oils by other manufactures that do use the "W" format.