Hi, 06XL1200C with 3,000 miles on it. Dealer Serviced at 1,000 with H-D Syn3 . Want to change over to Mobil 1 and decided on Mobil1 car 15w-50 with 5,000 oil/filter changes for the primary. Going Mobil1 75w-90 in the tranny . The question is I have a quart of MB1 75w-90 treated with Guard Dog Moly Treatment for 75w-90 syn gear oil , it is a moly additive. Will this benifit the tranny or possilble cause any damage. Wether it's worth it or not is moot as I already have a quart mixed for My totaled VTX just sitting here and only 6 months on the shelf, hate to waste it and its a great Moly additive. ...................WVleo

 

The tranny and primary both share the same fluid on a Sportster. I used the Mobil 1 V Twin 20W50in the primary/tranny and also in the engine whenI had my Sportster. Not sure if by saying primary you meant the engine oil.

 

Mobil-1 15w50 works great in the engine crankcase. Mobil-1 75w-90 Gear Oil works great in the combo Tranny/Primary, but you DO NOT want anything with a Moly additive in the Primary/Tranny, it's bad news for the clutch.

 

Yes I believe engine ............WVleo

 

What Charley said ... X10

 

Hi, OK, I know the moly and the clutch don't mix and now I know were the clutch is LOL ! Only have the Clymers manual downloaded to my hard drive. Thanks guys I'll get some new Mobil1 75w-90 for the clutch and tranny . ........WVleo

 

There's a oil and tranny section for researching this stuff, if you really want to see alot more posts on this subject.

I run Mobile 1 in my engine, but was told to use tranny primary/tranny fluid for the primary and tranny, that the only reason that Syn 3 can be used in all holes is cause it was specially designed for all holes on the harley. Special ingredients. But then I'm no chemist and can't really give you a rundown on what it the actual truth or fact of the matter.

 

Hmmm, I don't know how you came to this conclusion if you really read through the Oil section. Yes, you can put Syn 3 in all the holes, but you can do the same with Mobil-1, Amsoil, Redlineetc., but they are all formulated as Engine Oils not Gear Oils.

Buy the way, HD no longer recommends the one oil in all holes idea. It recommends Formula+ (a Gear Oil) in the tranny.

 

I run Castrol Syntec 20-50 in the engine and Mobil 1 75-90 in the tranny of my 01 Sportster Sport. 7 years and not a problem. I do remember the shifting was much smoother after the change to Mobil 1.

 

syn is harley spec citgo produced junk, castrol syntec isnt really a pao full synthetic, just highly refined dino, mobil or better yet amsoil are the way to go. there are some very informative articles on lubricants on line, i have been using amsoil v-twin 20-50 in both holes runs great and shifts better,amsoil uses NO friction modifiers