Motor Oil FAQ for Harley Davidson Owners

Whether you’re a seasoned Harley Davidson rider or a new owner, understanding the intricacies of motor oil selection is crucial for maintaining your bike’s performance.

With different sumps for motor oil, primary fluid, and transmission fluid, choosing the right lubricant can seem daunting.

Here, we’ll address some frequently asked questions about motor oil for Harley Davidsons.

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Most Common Motor Oil FAQs for Harley Davidson Owners

Here are the frequently asked questions about Harley Davidson motor oil…

1. Why Does a Harley Have Three Sumps?

In many models of Harley Davidson and other kinds of motorcycles, the engine contains three separate sumps: one for motor oil, one for primary fluid, and one for transmission fluid.

It wasn’t always this way, however. Originally, Harleys relied on manual application of lubricating oil into engine intervals to keep the engine from seizing.

It wasn’t until 1936 when Harley attached an oil pump to the engine that lubrication was mechanized.

This is one reason why Harleys have dry sump engines rather than wet sump engines.

2. What Is the Difference Between a Dry Sump and Wet Sump Engine?

A wet sump is a lubrication system wherein the primary oil reservoir serves to collect oil beneath the moving parts of the engine.

A dry sump system is when the oil is kept in a separate reservoir and the pan is pumped “dry.”

Most commonly, cars tend to have wet sumps while motorcycles tend to have dry sumps.

3. Benefits of a Dry Sump System

Why is it that motorcycles have dry sumps?

Well, it turns out there are some key benefits to a dry sump system when it comes to drivability and maintenance.

Here are some of the benefits of the dry sump system of a motorcycle:

  • Dry sumps generally have a larger reservoir than wet sump systems. This is particularly helpful when the motorcycle is navigating sharp corners, as it’s easier to keep oil in contact with the necessary parts of the engine.
  • Better center of gravity. Because dry sumps generally have a shallower oil pan relative to a wet sump, the engine can be mounted lower on the motorcycle. This improves drivability as it lowers the center of gravity.
  • Improved ring seal. Because of the extra vacuum created by the dry sump crankcase, the ring seal is secured, reducing windage and keeping all moving components of the rotating assembly lubricated.
  • Consistent oil pressure. The dry sump system offers consistent, adjustable oil pressure so motorcycle owners can “dial in” performance.
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4. Can I Use Car Engine Oil in My Harley?

If you’re really in a bind and you just need simple lubrication for your motorcycle, you may be able to use car engine oil temporarily.

However, if used repeatedly, this may cause damage to your Harley, as motorcycle oil has extra lubricants and frictional additives which optimize it for motorcycle performance.

5. What’s the Difference Between Primary Fluid, Transmission Fluid, and Motor Oil on a Harley?

So, if there are three sumps on your Harley Davidson motorcycle, what purpose does each one serve?

And if all three sumps are collecting some kind of lubricating oil, can you use one motor oil for all three Harley sumps?

The truth of this matter comes down to personal preference.

For some, it is inadvisable to put anything other than primary fluid in the primary fluid sump, because it was designed with primary fluid in mind.

Others know that primary fluid is similar in viscosity to SAE 50 motor oil and, in a pinch, this can work instead of lubricant branded for this particular sump.

When it comes to transmission fluid, generally a higher viscosity lubricant than 20W-50 is recommended.

This optimizes performance in cold weather, boosts fuel economy, and improves gear transitions.

However, some don’t mind hearing the “clunk” of a transitioning gear or don’t have to worry about cold weather.

For those people, one motor oil for all three sumps may be sufficient.

Motor Oil FAQ for Harley Davidson Owners

6. Can You Use 20W-50 Motor Oil for All Three Sumps on a Harley?

Depending on driving conditions and driver preference, you might be able to use 20W-50 motor oil for all three sumps.

However, for optimal performance, using tailored lubricants for each sump is recommended.

7. Can I Use Synthetic Motor Oil in My Harley?

Yes, synthetic motor oil is an excellent choice for Harley Davidson motorcycles.

Synthetic oils offer superior protection and performance compared to conventional oils, especially in high-temperature environments common to motorcycle engines.

8. How Often Should I Change the Motor Oil in My Harley?

Harley Davidson recommends changing the motor oil every 5,000 miles for most models.

However, this can vary based on your riding habits and the specific model of your Harley.

Consult your owner’s manual for the manufacturer’s recommendations.

9. What Are the Benefits of Using Synthetic Motor Oil in My Harley?

Synthetic motor oils offer several benefits for Harley Davidson motorcycles, including:

  • Better engine protection at high temperatures
  • Improved lubrication during cold starts
  • Reduced engine wear and tear
  • Longer oil change intervals compared to conventional oils

10. Should I Use a Specific Viscosity Grade for My Harley Davidson?

Harley Davidson typically recommends using 20W-50 viscosity grade motor oil for most models.

However, it’s essential to check your owner’s manual for the manufacturer’s specific recommendations, as some models may require different viscosity grades.

11. Can I Mix Different Brands of Motor Oil in My Harley?

While it’s generally safe to mix different brands of motor oil, it’s best to stick to a single brand and type of oil for optimal performance and compatibility.

Mixing oils with different additive packages can potentially lead to reduced performance and engine issues.

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Choosing the right motor oil for your Harley Davidson is crucial for maintaining its performance and longevity.

By understanding the different types of oils available, their benefits, and following the manufacturer’s recommendations, you can ensure that your Harley runs smoothly for years to come.

If you have any doubts about which oil to use, consult your owner’s manual or seek advice from a qualified mechanic.

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