Forgive the newbie questions:
Manual says to use a 20w-50 diesel type engine oil. I found Castol GTX at my local Advanced Auto store, but it looked like it was only for gasoline engines. When the H-D brand oil is not used, what should I be buying?

Also, can I us a 75w-90 gear oil in the primary/trans? Any favorite brands?

 

Redline products, Mobil 1 synthetic, Amsoil synthetic, all of these are excellent oils for your bike. Mobil 1 is usually pretty easy to find at auto stores. some will tell you synth. is a waste of money . I have used both and synth runs way better in my book. Your mileage (and opinion) may vary.. good luck in your search. I have seen Lucas oil for motorcycles at the auto parts store as well. I haven't used it personally but all there products seem to work well. As for as weight oil to use in the trans/primary I am not sure what weight is best for you.

 

I think the manual says 15W40 Diesel oil if you cant find HD oil

Diesel oil is identified by the API rating of "C" something like I or J for todays oil perhaps CJ4 or just CI or CJ (the C means compression ignition)

Gasoline oil is identified as "S" followed by M or N mostly today (the S means spark ignition)

Yes you can run 75W90 in the primary

Check the Redline™ web site

 

Please, use the search function for the forum. It will have shown all these answers in a million other posts just like this, as well as using google to answer this question. That being said:

You can use any automotive oil in the engine as long as it is the correct viscosity for your operating temperatures. This is because the engine lubrication is isolated from the rest of the drivetrain, which means it is just like every other car engine out there.

For the transmission/primary, you need to use something that is both the correct viscosity and wet clutch compatible. HD recommends Formula+, which is essentially a GL1 gear oil. As long as it is 20W-50 engine weight, which is equivalent to 75W-90 gear oil weight, and is wet clutch compatible you will be ok.

You can use 75W-90 gear oil such as Mobile 1, but be aware that it is GL5 with Extreme Pressure additives that are proven to react negatively with yellow metals (i.e. stator wirings, shifter forks, brass rivets in the clutch). Mobile 1 themselves do not recommend it; they instead recommend 20W-50 V-Twin in the primary/tranny of a Sportster, which performs better than HDs Formula+ when it comes to wear and tear.

 

Great info all. Thanks for sharing the wisdom!

 

Bought Castrol 20w-50 for the engine and Valvoline 4 stroke motorcycle 20w-50 for the trans/primary. Neither are synthetics. Will these choices be ok?

 

Most wear and tear occurs when engine is not up to working temperature. Water-cooled engines have thermostats to keep the temperature under control. Air-cooled engines cannot kept in narrow temperature range, thus lubrication becomes an issue.
Synthetic oils are far superior to regular oil when it becomes cold/overcooled engines.
Pour nothing but full synthetic oil into your Harley.
In depth article about oils is here: http://www.ferrarichat.com/forum/faq...=haas_articles
A little lengthy, but worth reading.

 

I have a 2003 883r. I use Mobil 1 20w 50 V-twin oil for both holes. I was using the Mobil 75/90 gear oil in the trans.

But when my stator went bad I switched it to the 20w 50 V-twin oil

 

Yes. That's fine. I like the Valvoline 4-stroke motorcycle and run it in my Kawisaki that is a common sump system.

 

I used to run Syn3 in my '02R, Formula X in the tranny.