https://www.hdforums.com/forum/oil-archive-no-new-posts/18046-synthetic-oil-analysis.html

I stand corrected. According to the above thread 15w-50 does have some Moly in it. It has less than Mobil VTwin 20w-50 though HD's Syn3 doesn't have any.

 

M1 contains moly, which some say is not favorable for use in wet clutches. Regardless, a high-tech oil like M1 is not necessary for the primary. I run Castrol GTX 20w50 and it is perfect for that location, costing <$3/qt. at Wal-Mart.

 

I use Mobil 1 15w-50 in the motor and primary, $23 for a 5 qt jug at Walmart. No problems here in the 20000 miles I've been using it.

Steve

 

I've used the standard Mobil 15W-50 in the primary for years, never had a problem.

 

Yes, I've been running GTX 20w50 in my primary, but I'm changing to Mobil syn for two reasons:

First, it has been very hot here in Oklahoma. A Harley mechanic told me that synthetic in the primary would help reduce the heat.

Second, I changed the primary when it was still warm and I noticed the oil was foaming a little. I understand that Mobil synthetic resist foaming a little better, so I going to give it a try.

Thanks everyone for your help and comments.

Beary

 

There is relatively little heat issue in the primary, and little to generate heat. The clutch disks do create friction when engaging, but there should be little once engaged. The chain also should generate little heat. That said, let us know if you see a difference, but I don't know how you would quantify it. Next time you change the primary oil dip your finger in it. You should notice that it isn't particularly hot. Next time I change mine I'll check with a thermometer. The environment is far less stressful in the primary than in an engine, and any fossil oil should be able to deal with that environment.

Foaming should not cause problems in the primary. Again, it is there for one purpose, to cool the chain and clutch disks. A little air in the mix isn't the same concern there as it would be in the engine, IMO. I've never noticed any aeration on my bikes.

 

You guys are really overthinking this oil in the primary issue. As iclick says, the main purpose of the oil in the primary is to help cool the chain and discs. I run Dexron III ATF, and use the cheapest stuff I can find, usually about a 1.69 a quart. Any good oil will work in the primary and those without friction modifiers are preferred.

The engine is a whole different matter and depends on the use - severe is high temps and high HP. I am currently running Mobil 1 20w-50, before that ran a 25w-60 dino oil and next am going to try some Redline 20w-50. The only difference i can see is that the 25w-60 ran a touch hotter, and consumption in 5k miles was about 3/4 qt. The Mobil 1 synthetic runs about 10 degrees cooler and comsumption was less than 1/2 qt in 5k miles. Oil is one of those "personal" things and some will swear better performance over others, but when it comes right down to it, all are very similar.

 

This leads to a question I've been wondering, why does synthetic run cooler?


Beary

 

Dalton is right on the money. If you think about what is in an automatic tranny. They have bearings, gears, some type of friction material(discs or bands) and front wheel drives have chains. We run these for thousands of mile in our cars and trucks towing and otherwise abusing them and have very few problems. In your primary which has far less abuse and is changed much more frequently you will have no problem.
It's funny before the all mighty Harley gods said " USE THE SAME FLUID IN ALL THREE HOLES" you had a hard time convincing a customer to put anything but motor oil in the engine, primary fluid in the primary, nad gear oil in the tranny, but now it's alright!!!

 

In the primary, you should have a oil that says it is ok for a wet clutch.
Some choices are, AMSOIL 20w-50, AMSOIL Motorcycle 20w-50, Mobil 1 v twin 20-50, Syn3 or formula plus. I have used all of these.