Oil change
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,586
Likes: 6,435
From: Honah Lee
I personal think it was due to the fact that for years, quality motor oil has detergents in it to keep contaminants in suspension to be caught by the filter.
The primary and transmission do not have a filter. That magnet on the plugs does indeed catch metal particles but it's intention is mainly to show bearing failures. In the unfiltered boxes, you are better off with a straight weight gear oil that lets crud sink and stay on the bottom. Problem is Harley's Formula + gear is one of the few 50W gear oils that is not GL5. Do not use an auto GL5 90W in there. It's way too thick to lubricate and flush those double row small needle bearings in the input shaft
If I were you, use the latest spec on what Harley has for it's latest engineering for lubrication. Think they found out the hard way motor oil is not number one.
However, 99% of cases, it will not matter for motoroil in all three.
I have used Formula + in mine for 50K along with 15W-50 Mobile 1 in the motor and it runs like new. However, I don't run in 100 degree heat either.
Tourer
Joined: Feb 2009
Posts: 354
Likes: 119
From: Penna.
I've used synthetic oil in the entire bike since day one and I have over 105,000 miles on it now. Never had any problems, clutch or otherwise. I think the synthetic has actually extended the life of the engine. The engine has great compression and is chugging right along!
Novice
Joined: Oct 2015
Posts: 16
Likes: 4
From: Eugene
Works great in engine for sure. Do recommend a heavier oil for tranny - did have some clutch slip with syn in primary but had just done stage 2 - added vpc clutch and all good. Did 95ci on my NT with ~55000 miles on it tat had Synthetic ever since break in and it still had all the crosshatching in the cylinders... might work a little too well...
Big Kahuna HDF Member
Joined: Dec 2012
Posts: 322,622
Likes: 3,077
From: .....
I don't like synthetic because it ticks like hell because it's thinner than regular oil. It's supposed to "last longer" than regular oil but to me, that's the only good thing.
Seasoned HDF Member
Joined: Sep 2013
Posts: 6,175
Likes: 1,966
From: Great State of Canada
Its not thinner at operating temps though. Thats the key.
Extreme HDF Member
Joined: Jan 2012
Posts: 12,986
Likes: 715
From: NE Philly
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Big Kahuna HDF Member
Joined: Dec 2012
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From: .....
