Not just "another" oil thread! lol A performance mod, primary oil thread!

M8 has been out for what, 8 years? Lots of us have done performance mods, Stages or Custom. And yet I can't get a straight answer what to use in the primary for a power uprate. Supposed experts have told me completely different recommendations, which is impossible. Maybe I should just mix a bunch of different oils together and throw the alchemy blend in there & patent it.

Dealer sez the new-ish Heavy Gear Oil 80W-140 is da bomb. My performance builder says it's crap for wet clutch....will drag and not shift right. WTF, MAN?

Anyway, even before my Stage III build, I tried Red Line Primary Oil, but that made the clutch plates squeak during engagement. Seems to me that's insufficient lubricity. But they did not squeak with the factory oil fill, whatever that was. The fact the primary has chains, roller bearings, clutches, and the infamous compensator ramp means different things. The comp ramp has a sliding surface so should need heavy oil. Stacks of wet clutches should need friction modifier additive for smooth no-squeaking engagement.

What do you performance mod people use successfully?

 

Everything. And nobody's bike blew up because of one brand or another

 

Interestingly seen on here the 80W-140 is rated differently than 15W-50 motor oil and the old standby Formula plus which is a straight weight 50W gear oil that is being phased out.

Look like Harley needs to add a few more holes. Then they can call out a 5 hole change...

I can see a 80W-140 in Florida in the summer. Sure not where you live.

Brandon is a qualified oil engineer on here. Just poked him for you. I would avoid the witch brews.

AI....
80W-140 gear oil and 15W-50 motor oil are not the same; 80W-140 is a much thicker gear lubricant for transmissions and differentials, while 15W-50 is a lighter engine oil for motor lubrication, but they can sometimes be used interchangeably in specific motorcycle components like transmissions where their operating viscosities overlap, with 80W-140 being much thicker when hot (140 vs 50).

According to Petroleum Service Company and ADDINOL. The "W" denotes winter (cold) viscosity, while the second number is the hot operating viscosity, so 15W-50 flows like a 15 weight when cold and a 50 weight when hot, while 80W-140 flows like an 80 weight when cold and a 140 weight when hot.

@BrandonSmith

 

So, "feed 'em what's on sale"? Everything's good?

'K

 

I run 30wt non-detergent in my primary. I have in all three of my ElectraGlides. 1989/2002/2019

 

Yeah, back in the day I was a trained Mobil Oil Industrial Lube Engineer, so I know a few things. But I didn't design the damned kluge inside the primary case, so all I can do is generalize what different elements are present and what lube characteristics each needs not to wear too fast. Then stir in adding +20% more power, and I thought somebody, somewhere has experimented and knows what works.

Then I get stuff like "feed 'em what's on sale". Wonderful. I don't need blown up ramps stranding me.

A so-called build 'expert' blew up my Stage III engine previously, too.

 

I run Lucas 75w140 VTwin, and i do not baby the 128. I do have SE Clutch Springs and the AIM pressure plate, the horror stories about the synthetic gear oil taking out my clutch are just that...stories.

The Lucas is rated for clutches, but my buddy runs the "non V-Twin" Lucas 75w140 Synthetic, and has nearly the same 150 lb/ft built as mine, and twice the mileage. No issues.

I love the gear oil in the trans and primary, and will never switch back

 

I'm not a true performance mod guy (just a cam), but I've tried a bunch and for clutch feel and all around wear/protection I keep coming back to good ole Formula+ - and I don't change it for 10,000 miles like the book states. Just works.

 

Thanks NW. I tried the heavy gear oil in the trans also and it shifts better and finds neutral better than RL Shockproof.

 

If you are worried about the lack of friction modifiers in the oil, Chrysler and GM sell it for the old clutch style posi traction rear end units.