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Not really another my oil choices are better than yours thread but a question:
General Topics/Tech TipsDiscussion on break in periods, rider comfort, seats and pad suggestions. Tech tips as they become available will be posted here.
Not really another my oil choices are better than yours thread but a question:
I was just changing my oil midseason/lateseason - I was only changing the engine oil after 3,000 or so miles - not the trans or chaincase - until spring when I change everything - and was wondering something:
Why do Harleys with 3 seperate oil compartments need motorcycle oil in the engine - when the transmission is seperate?
Googling it, I couldn't even get AI to understand the question.
With my Honda the engine oil and trans oil is the same thing in the same compartment. So they don't want any automotive type friction modifiers in the engine oil as it's also the trans oil.
But Harley engine oil and trans oil are seperate, why not friction modifiers in the engine oil like a car?
I realize you can use the same oil in all 3 holes but I don't.
20W50 engine, 70w140 Spectro in the trans and Belray chaincase oil in the chaincase.
So why not automotive type friction modifiers added oil in the engine?
Why motorcycle oil?
Sorry for the long *** post but I wanted to be thorough and avoid the responces thinking I was asking why the trans doesn't want friction modifiers.
Many of us run automotive engine oil in the engine.
Ah, I thought so! It should be better - but you won't find that written anywhere, owners or service manual.
So why doesn't everybody do that?
I am new to Harley-Davidson.
I also thought it was odd when I inquired at my local dealership about an oil change price (just for kicks- $280!) and found they use the same oil in all three holes.
Last edited by Robertbc3141; Aug 31, 2025 at 10:19 PM.
There are 100s of threads for you to pour over, here. There is a now-closed, read-only oil subforum. No subject has more controversy than oil.
That question you asked there sparks more arguments than your posted feelings about Amsoil and cheap tires. There are many that believe motorcycles should have motorcycle oil in the engine, and that it is more special than just the clutch modifiers.
I just happen to believe in my knowledge of the internal combustion engine, and choose to run engine oil. The primary has the clutch, it gets something different.
No harm, no foul. Run what you love. There are no posted failures of any kind from using any suitable oils.
FWIW....
Most the people I know & ride with, especially those that work on their own bikes, use a motorcycle oil (synthetic or conventional) in the engine, a gear oil in the transmission, and a non-detergent conventional oil in the primary.
Most of the name brand motorcycle oils have a different additive package than their regular automobile engine oils. These additive packages are designed to help the oil stand up to the extra heat in an air-cooled motorcycle engine. Their additives effectiveness is usually accepted, but the need for that extra protection is often debated.
IMHO...... With a 3000 mile change interval, and with the quality of all of today's oils, you won't have any issue running a brand name automobile engine oil.
Thanks - I again just asked Google "can I use regular automotive type oil in my Harley-Davidson engine" and got this:
"No, you cannot use regular automotive engine oil in your Harley-Davidson engine because it contains friction modifiers that will cause your wet clutch to slip and can damage it over time".
I just wonder how AI thinks it's getting into the trans - it's got to be assuming you're using the same oil in the trans.
And I meant no disrespect calling Dunlops cheap tires, while they are less expensive than Shinkos they are not cheap tires.
Last edited by Robertbc3141; Aug 31, 2025 at 10:44 PM.
FWIW....
Most the people I know & ride with, especially those that work on their own bikes, use a motorcycle oil (synthetic or conventional) in the engine, a gear oil in the transmission, and a non-detergent conventional oil in the primary.
Most of the name brand motorcycle oils have a different additive package than their regular automobile engine oils. These additive packages are designed to help the oil stand up to the extra heat in an air-cooled motorcycle engine. Their additives effectiveness is usually accepted, but the need for that extra protection is often debated.
IMHO...... With a 3000-mile change interval, and with the quality of all of today's oils, you won't have any issue running a brand-name automobile engine oil.
I've always heard that you'll never harm an engine by running too clean an oil. It may cost you more, but it won't cost you an engine. As with many things in life, continue to do your research, ask thoughtful and inquisitive questions, and then find your own level.
Originally Posted by Robertbc3141
Thanks - I again just asked Google "can I use regular automotive type oil in my Harley-Davidson engine" and got this:
"No, you cannot use regular automotive engine oil in your Harley-Davidson engine because it contains friction modifiers that will cause your wet clutch to slip and can damage it over time". I just wonder how AI thinks it's getting into the trans - it's got to be assuming you're using the same oil in the trans.
A clue is in its name: "artificial" intelligence! It pulls what it finds on the 'net and regurgitates it back out as an answer. The old adage still holds true, 'garbage in, garbage out!'
OP, go here and start with the Sticky Threads. Those should answer all of your oil questions. If not, there are 4,888 threads with 47,836 posts. Those should keep you busy for a while.
7 Surprising Harley-Davidson Products that Are Not Motorcycles
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Not really another my oil choices are better than yours thread but a question:
