I have a 2005 flht. Previous owner told me he ran all synthetic fluids. I am swapping clutch cable so went to local hd for a new gasket and gave him the info at hand. He came back with 1qt of synthetic engine oil. Is it an okay practice to use engine oil instead of the transmission fluid discussed in the manuel? I know my old ironhead sportie its one and the same. Just want to make sure its okay in this bike as well. Sorry if this is a dumb question.

 

I've been running Syn3 in all 3 holes with no problems.

 

when the twincam was first released, syn3 was spec'd for motor oil, primary lube ( clutch) and transmission.
( oops! this is incorrect- see post below! )

some feel that the syn3 didn't protect as well in the gearbox ..or provide as good clutch action.

the aftermarket and Harley sell tranny and primary specific lubes.

I use the HD Primary+ and it works for me.

I tried redline in my evo tranny- no difference but the red dye could help if you were tracking a leak ( kinda like why auto transmission fluid is red)



Mike

 

Exactly what I was thinking. Thanks for the quick answers guys. This forum is the best.

 

Believe me or not.

I use Mobile 1 15w50 in the engine .. Redline Shockproof in the transmission
and Redline Primary oil in the Primary.

My 2005 Road King has 127K on it and it's never seen the inside of the dealer shop. I did do cam tensioners at 70K.

I will need to do a top end eventually as I'm getting some oil going through the front cylinder valve seal but it basically still runs good.

 

The twin cam debuted in '99. syn3 was not available until '03. But to answer the OP question, HD recommends Formula+ or Syn3. But many others recommend other stuff.

 

Here is a good read on the subject. Motor oil will work but I don't know why you would use it when there are better products out there. I wouldn't hesitate in a pinch.

http://bakerdrivetrain.com/wordpress...Drivetrain.pdf

 

Some folks use ATF in their primary, the red color and it's cheap.

 

Even though H-D (and the dealerships) uses and recommends SYN3 for the engine, primary and transmission, I prefer to use Redline Shockproof in my transmission.
I also tried Redline 20w-60w synthetic motor oil in my '13 CVO 110 engine this summer, and perhaps it's just my imagination, but I think my engine was a little quieter (not as much ticking) than usual.

 

Mobil 1 V-Twin 20w50 Syn in all three holes.
Sweet, simple, and readily available.
Read for yourself...
https://mobiloil.com/en/motor-oils/m...motorcycle-oil