I'm about to switch my Breakout over to Synthetic 15-50 for Winter, and wonder if anyone else is running this type. While it's impossible to get the specs on Harley's Syn3 20-50, the specs for Amsoil & Mobil1 are available, along with he specs for each brands' 15-50 product.

At about 100 degrees F, 20-50 has a viscosity of about 150-175 and 15-50 has a viscosity of about 125-130, and those numbers only get higher as you go lower in temperature. At 212 degrees F, 20-50 has a viscosity of about 20, while the 15-50 comes in at about 18. Of course, as before, as the temperature goes higher those numbers drop even more, which is why running hot is bad for your engine.

Of course this has only addressed fully synthetic oil, not "Dino" oil. Why?... Because "Dino" oil will allow more damage to your engine during startup than the same weight Synthetic oil. Even with the same rating, Synthetic will have a lower viscosity at lower temperatures than a "Dino" oil, so it will actually start circulating through your engine sooner, lubricating it. And at operating temperatures the Synthetic will have the same viscosity (18-20) as the "Dino" oil, without the need for Viscosity Improvers.

How many times have you heard "Synthetic or Dino, it doesn't matter, as long as you do regular oil changes?" They're right - as long as you leave your engine running all the time and never shut it off. But once you let your engine cool off, that argument becomes false. Synthetic oils greatest strength is it's ability to flow sooner than Dino oils and protect your engine during startup.

So, now where was I?... Oh yeah, who's running 15-50?

 

I just use M-1 V-Twin 20-50 in all three Year round...... just me.. I wont use an oil made for cagers when they make oils MADE for motorcyles... $12. more for 3 qts of the V-Twin stuff isn't going break me...

 

I'm doing non-synthetic 20-50 and have for 18 of the 23 months I've had my bike. It gets cold here but I normally don't ride when it's below 40°.

 

You do realize that your non-synthetic oil has a viscosity over 170 when the engine is cold? At 40 degrees your oil probably is like trying to pump molasses through the engine. There's a tremendous amount of misinformation as to how oil works, and even what the figures on a can of oil mean.

 

It's probably OK, as long as one takes it really easy until the oil temperature comes up a bit. Which also isn't a bad idea in warmer weather. Engine parts don't reach their design tolerances until they come up to operating temperature, and cylinder wall wear is much higher at lower temperatures.

 

there should be NO debate as to which engine oil genre is best. Synth has won every time in laboratory tests since its introduction.
Maintains a consistent level of viscosity and protection at every start up and during every mile thereafter.

That said, you can go with synth 20-50 in all three holes year round.
But if you follow the old school theoretic standard. Than I suggest the use of proper weights accordingly; such as 10-40 for primary and 75-90 for the tranny. All synth of course.

Only question remains is which periodic change interval to abide to? Quick answer... YMMV
In my case or opinion, synthetic lubes are designed with indefinite break down properties that are meant to perform at their peak for the life time of use. One basically needs only to top of occasionally. BUT! And this is a real big butt. Oil filter will plug up. In which case, you might want to just go ahead and change the 20-50 in the crank. That's my $00.02 on the matter

 

I don't believe the theory that synthetic "will actually start circulating through your engine sooner, lubricating it". Your oil pump does not know whether it is synthetic or dino. It will pump oil no matter what is in the tank.

The first number in oil indicates the weight when cold or "winter". The lower it is, the easier it is to flow when cold. That is what you should base your decision on, and go with the 15w-50.

I have never understood why it is recommend to use engine oil, in a transmission. It does not have the shear properties as gear oil.

 

Go back and read my original message - synthetic oil viscosity is lower than dino oil at room temperatures and below for the same grades, period. It means that the synthetic oil will lubricate your engine better, quicker, than dino oil at startup.
It's a FACT. Just because you don't believe it doesn't make it untrue.

I personally use Redline in mine, and run a dry Primary.

 

Just ride the bike man, and quit sweating the small stuff.

That nano second of lubrication you state that synthetic has over dino, really doesn't matter in the grand scheme of things. You probably won't keep or ride the bike long enough to matter.

Many bikes out there running Castrol GTX with over 100k on the clock. Do a search for yourself.

 

I run 15-50 Mobil 1 all the time. Book compression at 45K is right where it was at 10K. Pretty obvious it's not hurting it but I drive easy. Where are you coming up with your viscosity numbers. I had assumed they measure it in drips per minute thru a calibrated hole. Would not a 15-50 be higher? Most of the times, my temperature dipstick runs 180-190 in summer and 150 in the winter. (I stay local and rarely drive when it's below freezing since I retired)