Both Amsoil and Mobil 1 V-Twin are good 20W-50 synthetic oils, and both are rated JASO MA and can be used in both the engine and in the tranny/primary for wet clutch applications.

 

The only difference I have noticed in 12000 miles is the cost of the stuff. Will probably go to Havoline 20-50 or Chevron 20-50 next change. Just my 2 cents.

 

Guess I'm different, but I don't feel the additional cost of running good synthetic oil is that big of a concern.

The cost of 3 quarts of Mobil 1 20W-50 V-Twin and a 63796-77A filter is what, maybe $30.00??

That's less than the cost of a carton of cigarettes or a night out at your local 'watering hole'..

 

I don't run syn. but thats my preference and I change oil every 2000 miles since majority of my riding is in town back and forth to work. Maybe the question is which syn. oil would anyone recommend. I say stay away from HD syn. but amsoil is a good one to use. HD doesn't even recommend using thier syn. in the primary anymore. At least my local dealer told me that.

 

There is a sh*t-ton of oil information posted on that forum and elsewhere on the web. I encourage you to check them out and decide for yourself.

Basically, synthetics resists breakdown in high heat (ie air cooled engines) and degradation from shear better than dino oil. There are labs that can test used oil for about $30 as sample. Some guys submit their used oil for analysis, and the posts I have read indicate the synthetics aren't beginning to degrade until around 7K miles of V-twin use.

As far as other claims, I have heard people say use of synthetics makes their engine quieter, louder, cooler, hotter, etc. In reality, I think those aren't very scientific observations.

If you hunt around, there was a very good post by poco regarding additives in engine oils, how they work, and the amounts in various brands. Pretty interesting stuff.

Anyway, I use Mobil 1 15-50 (not the V-twin) in the engine, Mobil 1 synthetic gear lube in the tranny and HD primary oil in the primary. As I remember, the V-twin has less friction modifiers in it than the yellow-capped extended use. It's my understanding that was done so it can be used in the primary without wet clutch slipping. Since I don't use it in the primary, I'd rather have the extra friction modifiers in the engine. Besides, it's a bunch cheaper than the V-twin.

Remember, for every oil opinion, there will be a counter-opinion and the bottom line is this - no engine ever blew up because someone used the wrong brand of oil.

Let your conscience be your guide.

 

True, the Mobil1 V-Twin 20W-50 (and Amsoil) both the the JASO-MA rating, which means they contain no friction modifiers and can be used for wet clutch applications. A JASO-MB rating means the product does contain friction modifiers.

That being said, I think people worry much more than our bikes do about the specific type of oil being used.

My old high mileage Shovelhead has run nothing but straight 50 and 60 weight oil it's whole life, and it is perfectly happy.

One of Harley's recommendations is to run straight SAE 60 weight oil in the Sportster EVO engines when the outside temperature is above 80 degrees, but most people just run 20W-50 year around.

One thing different with the Sportsters is that, unlike the Big Twins, the tranny and primary share the same fluid, so you can't run a seperate fluid for the engine, transmission, and primary.

Most of the folks I know that own Sportsters run the Mobil 1 75W-90 gear oil in the Sportster primary/tranny, and a good quality 20W-50 in the engine. But during the hot summer months (which around here can be 100+ for weeks on end) some switch over to SAE 60 for the engine.

But with frequent oil and filter changes you can run just about anything...

Like you said, I can't remember anyone ever having an engine/transmission/primary problem that was related to the fluid being used.

Most problems are caused by neglect, abuse, or just plain "operator" error.