HI everybidy, Im new here and I see this is a topic thats all over the place.
I have a 2003 flstci with the 88 motor.
it has 15k miles and I want to change the 3 fluids.
the main, the primary and the transmission.
can I just use the mobil 1 20w50 vtwin synthetic oil in all 3 holes or do I have to use the special oils for each. This is my first time working on a Harley and I dont want to eff it up.
Also, for my bike, how much oil in each hole?
and I will have a new filter also.
I looked in the owners manual, it doesnt say how many ounces of oil for the primary or trans.
Thank you,
Eric

 

That will work, but IMHO, it is not optimum....

And if I may suggest, if you are going to work on your bike, you should get an HD Service Manual for your year/model bike... it will give you almost all the info you will ever need.. Much better than off brand manuals


On the topic of oil, FWIW:

I use a synthetic oil for the engine, because it's air cooled. Synthetic oils withstand higher heat better than a dino oil. I currently use Motul 7100 20W50 in my engines.

I use a non-synthetic primary oil, because most performance shops recommend against using synthetic in the primary, especially in higher HP applications. In the primary, I use Bel-Ray Primary chain case lubricant.

I use an 85W-145 weight, hypoid gear oil, for the transmission. I find it to be quieter than the use of an engine oil. In the transmission, I use Bey-Ray Big Twin Transmission oil.

I have transitioned through the use of several brands of oils. I started with straight 50W dino oil in my shovel heads, switched to Mobil 1 synthetic oils for many years, and have tried others over the years. All of the oils I used worked well, and I believe would still work today. I settled on my current choices for various reasons, but for simplicity sake, just call it personal preference.

Bottom line.... a quality oil in each application, with a proper oil change interval, I believe is more important than the oil brand. Oils have come a long way in that last 30 years or so. I can't remember the last time I heard about of a street driven engine that has failed due to the brand of oil that was used...


Related anecdote:
Before Harley offered a synthetic oil, they used to recommend it not be used in their engines. Then they came out with Harley Syn3 synthetic oil and all of a sudden, per Harley, it was the best stuff you can use. They recommended it for all three holes in their bikes. Now that Harley came out with a synthetic gear oil, they highly recommend that for the transmission and primary.

When the Syn3 came out, I tried it in all three holes of my 2003 Heritage. Within a month, I removed it from my trans because it became noisy in comparison to the gear oil I used to use. I never put it back in the primary, because I did some reading and found no other clutch manufacturer recommended a synthetic oil for their wet clutches (don't know if that's still true)

Welcome to the forum, you just started your first oil thread...

 

20/50 syn or non (dependent) crank
Form+ primary
Gear oil tranny

 

almost 20 year old bike..I'd just keep it simple and use the HD 360 for engine and Formula + in the transmission and primary

 

Most find synthetic oil will cause the motor to sound louder when riding. Running regular oil from the auto parts store will quiet that noise down, protection is the same, price is cheaper. Harley's primary oil will work fine, but costs more with no noticeable reason for it to cost more. Running 10/40 or 15/40 wt regular oil will work the same, but will not make the bike crunch badly into 1st gear. Also costs less. Running 70/90 or higher grade gear oil will make the trans quieter, and shift smoothly. You can use Harley's new gear oil, but the same grade at the auto parts store will be cheaper and perform just as well.,,

 

All three can be the Syn 3, or like an Amsoil MCV, or whatever brand you choose.

I'm an Amsoil guy personally. Change the oil filter too. Get the good guy funnels and oil tray. Get the service manual. Change the o-ring on all the plugs you remove. Initially, the cost sucks, but the second time you change the oil you're making money.

Personally - I run Amsoil MCV in the engine, Amsoil Primary, and Transmission in the specific holes. The new filter of course. Drain it while hot, allow it to cool, and change later.

If all you do at home is oil at 5000 miles, you're saving $150 each time. As stated earlier, the service manual is highly recommended.

Have fun,
H