I've only got two holes, LOL . . .

I run Moco straight (Dino) fifty weight oil in my EVO motor and Redline Heavy Duty Shockproof oil (synthetic) in the transmission.

Here's my thinking. Keeping in mind oil selection has to make you feel comfortable and you may think I'm full of baloney!

Multi-grade oil is a marketing myth: Do you think they add little "smart" molecules to it? "Oh, I'm hot now, I'd better start adjusting my viscosity!" All oils are thicker (less viscous) when cold and thinner (more viscous) when hot. So buying muti-grade is money out the window. We'll talk about valve train clatter in a cold climate in a minute.

I think synthetic oil manufactures (like AMISOL) hire more marketing guys than they do engineers. One fact they tout is your engine will run cooler due to less friction between the moving parts. However, the majority of the heat generated in a Harley motor is from combustion not friction. That's the heat you feel on your thighs. If you had a way to spin a motor up to 1000 rpm for a half hour without actually starting it how "hot" do you think it would actually get?

They also claim a longer oil change interval with synthetic. The truth is no matter what oil you use all motors eat themselves. If they didn't, or if synthetic oil really made any difference, motors would never wear out. When you increase the oil change interval all you're doing is circulating those metal particles through your engine for a longer period of time.

Synthetic oil is more corrosion preventing than Dino oil. Actually straight fifty weight is going to hang onto the top end of your motor (if you don't ride the bike for a long period) a lot longer than more slippery synthetic oil which will leak down. That's why motors using thicker Dino oil (and otherwise set up and maintained correctly never clatter.) Besides, rust (inside a motor) is an overblown issue and just the synthetic oil boys looking for something to hang their hats on. I've seen the insides of 30 year old motors, that look like hell on the outside, but look pristine on the inside.

I live in a warm climate, but even if I didn't I'd still run straight 50 weight Dino oil (like the 10 generations of Harley owners before me.) If you're in a colder climate, especially with a naturally (really should be called unnaturally) hot running Twin Cam that 20-50 muti-grade oil (synthetic or not) is going to turn into 5 weight sewing machine oil at operating temperature. And probably why some say their motors are unnaturally noisy.

Again, I have a EVO motor and like the Flat, Knuck, Pan, and Shovel motors before it heat isn't an issue. And while I've ridden the newer Twin Cams (and they are very sweet machines) synthetic oil, along with the rear cylinder shut down system, the add-on oil coolers, and the vents in your bagger fairing are just band-aids masking a much larger problem. Simply put 96 cubic centimeters is too much for an air cooled in-line V-twin. Properly set up I believe the motor can take it but it's pretty obvious, from a comfort standpoint, the riders can't. And that's the 900 pound gorilla in the room . . .

 

Same here! Amsoil 20w50 in all 3 holes. Bike runs much cooler and a lot smoother!

Shawn

 

The "smart" molecules are called polymers. They work exactly as advertised.

I like Mobil 1. Been using it in the aluminum engines for 21 years and don't see a reason to change. In my iron engines I like a straight 60 or 70 aircraft oil. Airplanes don't coast to the side of the road if an engine fails.

 

HD 20w-50.....no problems with the company stuff

 

+1 ....just changed all three holes the other day. First time using the 75/90 in trans and 20/50 in primary. I like it alot

 

Do you notice any better or worse shifting and clutch action with so and so's oil ?
And, does the engine and trans run any cooler ?
Bobby.

 

Amsoil 20W-50 in engine, Harley Forumula + in primary, Spectro 75w-140 in tranny..

 

Mobil 1 20-50 crank
Mobil 1 85-140 trans
HD prime in prime.

 

Amsoil 20-50 in primary and crank, 75-90 Severe Gear in Tranny.

 

Do a search you lazy turd. There are thousands of posts on this stupid question.