Is the Harley Syn3 100% synthetic oil? If not, can I run Mobile 1 v-twin 20w-50 synthetic in the motor, tranmission, and primary like you can the HArley Syn3? What oil is beter?

 

Syn3 is not a full synthetic oil, I recondmend Ams oil or Red Line oil they are a full synthetic oil and they have different blends for the primary and trans.

 

I used to run SYN3 in all holes on my Softail and Electra Glide. After reading all the oil threads, opinions and talking with some HD mechanics (off the record outside hearing range of their managers) I now run Mobil 1 20w50 VTwin in the engine, Harley Formula Plus Primary and Gear Lube in the primary, and Mobil 75w90 Synthetic Gear Oil in the trans.

There's lots of info on this forum on this topic. SYN3 is not bad oil butfor about the same price or cheaper, you can buy the Mobil VTwin at AutoZone.

 

Amsoil, Royal Purple, Mobile 1, and Red Line are all excellent choices. Use the one that's easiest for you to get. I don't use one oil for all 3 holes. I use Amsoil 20-50 Motorcycle oil in the engine, Amsoil Sever Gear 75-140 in the tranny, and ATF in the primarry.

 

Ditto what Bryan said, exceptI use HD Forumla Plus in the primary... as they know their clutches best,
otherwise full synthetic in the motor and transmission.

 

Using AMSOIL in the Engine & Trans - HD in the primary...

 

Syn3 costs $10/qt. while Mobil1 15w50 is $4-5, VT somewhere in between. Both the M1 options are better than Syn3, IMO, and the lower-priced M1 is every bit as good as the VT variant. From what I've seen Syn3 is not an exemplary lubricant, neither good nor bad, but is not worth $10/qt., IMO. Take your pick from the high-quality products available, which include Mobil 1, Royal Purple, Amsoil, Redline, etc. All will do an excellent job, so pick according to price and availability, or brand preference if you have one.

I believe gearboxes should use gear oil, 75w90 for 5-speeds, 85w140 for 6-speeds to suppress some of the noise. The primary does not need a $10, $5, or even synthetic oil. Any $1/qt. fossil engine oil (10w-30 to 20w50) from Wal-Mart will work fine. Some use ATF in the primary, and I can't see why it wouldn't work fine, too.

 

Running with Mobil 1 V-Twin 20w50 in the engine and Primary and Mobil 1 Gear 75w90 in the tranny all Full Syn.

 

As already stated SYN 3 is not 100% synthetic, I run Redline Heavy shock in the transmission/gearbox ( gear changes are much more precise and my 4th gear ( EG 2006 ) noise is all but dissapeared.
I run full synthetic ATF in the primary which has made a considerable improvement in clutch operation & smoother gear changes.
As far as the motor goesany good dyno or synthetic will work fine as long as you change regular ( 3000miles ).
There has been a lot of discussions on oils in this forum and it is becoming very confusing IE, DO NOT use car oils in m/cycles because they have friction modifiers in them which will cause problems with clutch operation. That may true in regards to metric bikes which share the same oil in motor,transmision &clutch but not in m/cycles such as HD as they do not share motor, transmission & clutchoils.
Thats my 2cents worth
lots of luck
Glenns glide

 

I have a small amount of Red Line Heavy Shockproof oil that I'd be happy to sell to anyone who'd like to give it a try - I no longer need it as I sold my RK a couple of weeks ago. The stuff sells for around $15 a quart (you need 1/2 a qt in the tranny) - make me an offer (email please - I'll sell individual qts). I have only 4-5 qts available. I used it in my tranny along with RedLine 20W50 in the engine and ATF in the primary for 15K miles.