I have a 1999 FXST and trying to figure out what fluids I need for the bike. I've seen back and forth about the primary and the transmission. From they take the same oil as the engine, to specific primary and transmission oil. Can anyone shed some light on this for me?

 

 

What he said.
I run 20W50 full syn in the engine and primary and 75W140 full syn in the trans.

 

there's as many opinions as there are riders....my experience with evo's is they didn't like syn oil in the engine....if there's a potential leak it will find it an sometimes it weeps from the base gaskets. I ran the walmart brand 20w50 or valvoline MC oil since it was high zinc. I just tried rotella in the primary an I really like the clutch so far but it's only been a few rides. I used the syn blend 75w90 in the trans of my evo...just put it in my '15 TC an it shifts nice. some swear by the big name big money oils but harleys are simple machines an the evo's are pretty low tech so I ran the cheaper brands an changed them more often. IF you do a lot of stop an go in hi temps you might want a better oil though. there's an oil section on the forum you can search.

 

A 99 Evo would probably do best with a straight 50 weight dude , Dino or Synth is on you.
Gearbox and primary could take HD-360 I guess.

 

Oil choice and oil recommendations can be as much marketing as anything else..... Harley always bad mouthed synthetic oil.... that is until they had their own synthetic-labelled oil... now they say to put it in all three holes... interesting..

My answer to your question: Yes, you can put the same oil in all three holes and get many years of reliable service from your bike....

But I don't/won't do that...

Since my first shovelhead, I have always use different oils in the the three different holes...

I prefer to use a quality synthetic engine oil (10W60) in the engine, been using HD Formula 1 or Belray Gear Saver (75W) in the primary, and a synthetic gear oil (75W90) in the transmissions.

I now do all my own services. It's not really that hard for me to keep a few different types of oil around...

I once tried the HD syn in all three holes of my '03 twin cam... didn't like it at all. I didn't like the way it shifted and the trans was really loud. I switched fluids in the primary and trans within 200 miles of that service...

I used straight weight dyno oils in my old EVO bike, but wouldn't hesitate to use the quality multi-weight oils available today... I prefer synthetics these days, in an air cooled engine, because of their higher temp ratings..

The key is to change the fluids regularly by miles or by time.....

I choose to go 5k miles engine & primary, and 10K miles on trans.... or, 1 year engine/primary & 2 years trans.... but you will get much debate over those parameters.....

Enjoy the bike!!

 

Got my first Harley in '01, dealer tech (a great dealer and tech by the way) said to use nothing but Bel-Ray 85-140 in the transmission, been doing it ever since. I put HD Formula+ in the primary and Syn3 in the motor. Before the days of Syn3 it was HD360 20W-50. It's always worked for me.

-jeff

 

What works for me...15W50 Synthetic Mobil 1 for engine. Harley's Formual + non detergent straight weight gear oil for primary and transmission. There is no filter, so non detergent is best. No one really has anything better for that spec.
I have 50K + on my 04 and it runs like new.