75w90 synthetic gear lubricant, thin enough to go through all the small passages quickly and thick enough to keep good viscosity. Change at 20000 miles intervals...not that complicated.

 

The majority of us throw away good oil every change...because it's dirty...it's the dirt that kills the engine over time...not "bad oil"...by the time you "wear out the oil" (~10,000 miles) it is unbelievably filthy and your oil filter is most likely totally plugged with the bypass open all the time.

Because of that, I'm a "change often" guy.

Your manual probably says "5000 miles under ideal conditions" and "change it more often if not ideal conditions" for the engine oil. None of us ride under "ideal conditions", so 5000 miles is way too far; I change every 2500...so I want an oil that won't break my bank.

Engine Oil
Mobile1 15w50 - It's at Walmart in 5qt jugs for ~$25...there's often a rebate that lowers it to ~$20 or less for FIVE QUARTS of full synthetic, good oil. Note: this oil is ONLY for the engine.

Primary
Mobile1 Racing 4T 10w40 or 15w50 - It's JASO MA/MA2 certified (that means it's great for your clutch). The JASO rating is very tough and is focused on motorcycle clutches..if an oil can't meet the standard, it's not going in my clutch.

That first gear clunk is parasitic drag; even though the clutch handle is in, the plates are spinning due to an improperly adjusted clutch and/or cold/thick/improper oil that is causing enough drag to keep the plates spinning...so when you put it in gear...BANG!

Transmission
Mobile1 gear oil in whatever weight is appropriate for your typical ambient air riding temps. Each bike is a little different, but transmission oil can go 5000 miles in my bike; it just doesn't dirty up like the engine and clutch.

We can argue all day long whether or not these are the "best oils"...but I think everyone will agree they are "very good"...and they're much more affordable than the "designer" brands...which is important to me as I change often.

PS.
The engine has an oil filter...the clutch does not...the clutch wears constantly putting monster sized abrasive particles into the oil...change the clutch oil often...I'm at 1500 to 2000 miles depending on the type of riding it's been through...city (more shifting) vs highway(less shifting)...and again, with "sales" and "rebates", the Mobile1 Racing 4T oil is $7 or less a quart and it doesn't even take full quart on a 103 engine.

Search youtube for "Delboy's Garage, Harley Softail Service #3, Clutch Adjustment" to get it done right.

 

Yep. Your gonna get a lot of different answers but my two cents.....redline shock proof. It’s what I run.

 

Spectro GL-5 for my transmission. Just mistakenly ordered the Spectro Gear Guard and will run it thru when I change the fluids soon....

 

I just did my 1000 mi change and put in Spectro 6-speed. It is a nice quiet running transmission oil for sure. It's also dyed red for some reason.

 

I do love these why oil to use threads. I'm not saying anyone here is wrong.
If you ask 50 guys on what parts or spec to use when fixing there bike they will ALL say use Harley-davidson OEM period. But for some reason when it comes to the oil for the 3 holes Harley-davidson is wrong. We all have strong opinions, they make many different brands and weight of oil because. WE like what we like because. I use Klotz synthetic 25w-60 in all 3 holes been doing this for 30 years and don't want anyone advice. This is what I use because it is. You should run what you like not what someone else likes. Klotz is red so when it starts to turn brown I change it in the engine that's around 5000 miles, in primary and transmission 10,000 miles.

 

"I use Klotz synthetic 25w-60 in all 3 holes been doing this for 30 years"

Klotz's CEO thanks you for doing your part in making his Bugatti payments for all those years

For the average Joe, there's not a lot difference in performance between the major oils...they must be replaced for the same reason...dirt!.

Doesn't matter if it's $100/qt or $5/qt...it gets dirty all the same.

Decades of caring for engines of all types...with no oil related failures...I can say with that experience behind me...buy an "affordable" oil and change it often.

"10,000 miles in the Primary"...no freaken way...that clutch is constantly shedding abrasive particles that go 100% unfiltered...by the time you hit 10k miles, you've got some seriously abrasive oil in there. It takes less than a qt to fill the primary...going 10K miles to save $5 on oil? (Moble1 Racing 4t).

I would love to see the lab results of 10k Primary oil...I'll bet the tech that runs that test wonders if their equipment is broken...your viscosity has got to be whacked and particle count is probably to high for the machine to count...lol.

When I buy used equipment, I always talk oil with the owner of that equipment...if a Harley owners tells me "10k miles between primary changes"....I'm walking away from that bike in a hurry.

 

Royal Purple 75W140

 

Formula + in the transmission.