Best Transmission Oil for Harley 6 Speed

Are you tired of experiencing lackluster performance and unreliable shifting from your Harley’s 6-speed transmission? It’s time to upgrade to the best transmission oil.

You’ll be amazed to know that the type of transmission fluid you use for the engine can greatly affect ride quality. Yes, it can. And for this, it is very important to use the right oil.

The right oil can provide smooth, consistent shifting and prolong the life of your motorcycle’s transmission. So, it’s time to buckle up and discover the top picks for the best transmission oil for Harley 6 speed.

5 Best Transmission Oils for Harley 6 Speed

We have compiled a comprehensive list of some of the best transmission oils for Harley 6-speed. Before moving to the in-depth review of these products, we make a table on them. If you’re in a hurry, then this table will help you to get some ideas.

ProductsKey FeaturesRatingPrice
Spectro Oil R.HDPG6 Heavy Duty Synthetic Oil1. Offers superior protection in extreme temperatures and conditions
2. Reduce deposits and wear
3. Helps to reduce engine noise
4. Last longer and give you maximum protection for your engine
4.7Check Price
Red Line 20W50 Synthetic Oil, v-Twin Transmission Oil1. Enhanced wear protection
2. High-temperature protection
3. Low-temperature flow
4. Easy Shifting
4.8Check Price
Red Line RED42804 v-Twin Transmission Oil1. Enhanced anti-friction properties
2. Increased cold flow
3. Superior shear stability
4. High viscosity index
4.9Check Price
Ravenol ATF 8HP Fluid1. Enhanced protection against wear and tear 
2. Improved viscosity-temperature behavior 
3. Improved oxidation resistance 
4. Enhanced anti-shudder durability 
4.3Check Price
Mobil (112812-4pk) Delvac Synthetic Transmission Fluid1. Outstanding cold temperature flow
2. Low foam characteristics
3. Enhanced wear protection
4. Nice proven performance
4.7Check Price

1. Spectro Oil R.HDPG6 Heavy Duty Synthetic Oil

Are you tired of constantly having to replace your heavy-duty engine oil due to its inability to withstand the rigors of demanding operations? The solution to your problem is here – Spectro Oil R.HDPG6 Heavy Duty Synthetic Oil.

This premium synthetic oil is engineered to handle the toughest of tasks, delivering maximum performance and protection to your engine. With its advanced formula, this oil offers exceptional wear protection, minimizes engine deposits, and withstands high temperatures, ensuring that your engine runs smoothly and efficiently for longer.

It also provides superior protection from oxidation and corrosion and helps reduce friction for improved fuel economy. Whether you’re an off-road enthusiast or a professional driver, you can trust this oil to keep your engine running at peak performance. Get the most out of your vehicle with Spectro Oil R.HDPG6 Heavy Duty Synthetic Oil.

What We Like

  • Compatible with all 6-cylinder engines
  • Enhanced detergency and dispersancy properties keep engines clean
  • High viscosity index for consistent lubrication in hot and cold temperatures
  • Unaffected by extreme heat

What We Dislike

  • Little bit pricey

2. Red Line 20W50 Synthetic Oil, v-Twin Transmission Oil

You’re tired of using subpar engine oils that fail to deliver the performance and protection your engine needs; right? Why not try Red Line 20W50 Synthetic Oil?

This oil is designed to provide maximum protection and can survive longer than conventional oil. It has a higher level of detergents to help keep your engine cleaner, and the synthetic formulation helps it resist breakdown and thermal breakdown. All of this adds up to improved engine protection, extended drain intervals, and improved fuel economy.

With superior lubrication, it helps to reduce friction and keep your engine running smoother and longer. It also helps to reduce oil consumption, making it a great choice for keeping your engine in top condition. If you’re looking for an oil that can handle the toughest conditions, then Red Line 20W50 Synthetic Oil can be the Best Transmission Oil for Harley 6 Speed.

What We Like

  • Provides superior wear protection
  • Offers excellent thermal stability and oxidation resistance
  • Compatible with most gasoline and diesel engines
  • Meets or exceeds industry standards for durability and performance

What We Dislike

  • Requires an additional chaincase oil purchase for large V-twin

3. Red Line RED42804 v-Twin Transmission Oil

If you’re looking for a top-quality transmission oil for your Harley-Davidson 6-speed, Red Line’s RED42804 v-Twin Transmission Oil is a great option to consider. This oil is designed specifically for use in Harley transmissions and delivers exceptional performance and protection.

RED42804 is a synthetic blend that offers superior viscosity stability and resistance to thermal breakdown. It also protects against wear and corrosion, and helps keep gears running smoothly. And thanks to its low coefficient of friction, it can help increase your bike’s performance.

If you’re looking for an oil that will keep your Harley running like a dream, Red Line RED42804 v-Twin Transmission Oil is definitely worth considering.

What We Like

  • Provides extreme pressure protection
  • Contains anti-foaming agents to minimize foaming and maximize oil life
  • Compatible with most V-Twin transmissions
  • Promotes smooth shifting operation

What We Dislike

  • Burnt out oil has a bad odor

4. Ravenol ATF 8HP Fluid

The Ravenol ATF 8HP Fluid is another excellent transmission and primary oil option for Harley 6 Speed. This synthetic lubricant reduces wear and noise, has superior oxidation resistance, and provides enhanced shifting performance.

It has the perfect viscosity which not only makes it ideal for a Harley 6-speed but also works great in other motorcycles that use ATF oil. Ravenol is also known for its anti-foaming properties, which helps reduce shear forces, keeping your Harley 6 Speed running smooth and free of unnecessary wear and tear.

This oil has superior lubricating properties that help keep your motorcycle running for longer periods of time without the need for frequent oil changes that can save you time and money in the long run. It is also biodegradable and non-toxic, making it good for the environment too.

What We Like

  • High viscosity index
  • High oxidation and thermal stability
  • Excellent anti-foam and air release properties
  • Compatible with seals and metals
  • Prevents clutch chatter and shudder

What We Dislike

  • Not suitable for use in other types of transmissions
  • Pricey option

5. Mobil (112812-4pk) Delvac Synthetic Transmission Fluid

If you’re looking for an impressive transmission oil that offers great performance and a long lifespan, then the Mobil (112812-4PK) Delvac Synthetic is the way to go. This product is specifically designed for Harley 6 Speed motorcycles and it has been formulated to meet the needs of this engine. It’s a fully synthetic oil that can provide higher levels of protection for extended periods of time.

This oil has a higher viscosity which can help with improved wear protection and longer service life. You’ll also get excellent lubrication performance in both cold and hot weather conditions. It also has oxidation stability that helps keep it from breaking down quickly under tough operating conditions.

It’s also resistant to foaming, which means it will stay in place without aerating or forming air bubbles. This oil features enhanced rust and corrosion protection, so your motorcycle will stay in tip-top condition with minimal maintenance. And finally, this product is fully compatible with all previous SAE viscosity grades and OEM-approved fluids.

What We Like

  • Provides excellent oxidation and thermal stability
  • Optimized frictional properties
  • Excellent protection against rust, corrosion, and foaming
  • Compatible with most seals and gaskets

What We Dislike

  • Expensive compared to other transmission fluids 

How to Choose the Best Transmission Oil for Harley 6 Speed

Choosing the right transmission oil for your Harley 6 Speed can be a challenging task. With so many different types and brands of transmission oil available, it can be difficult to know which one is best for your bike. To help you make the right decision, here are some tips to help you choose the best transmission oil for your Harley 6 Speed:

Compatibility: Always make sure that the oil you choose is compatible with your Harley 6 speed transmission. Check the owner’s manual or contact the manufacturer for recommendations.

Viscosity: Viscosity refers to the thickness of the oil. Harley 6 speed transmissions require a specific viscosity range, usually 20W-50. Make sure that the oil you choose falls within this range.

Additives: Some transmission oils contain special additives that improve shifting, reduce wear and tear, and provide extra protection. Look for an oil that contains friction-reducing additives and anti-wear agents.

Quality: High-quality transmission oils are refined to remove impurities that can cause damage to your transmission. Look for a brand that has a good reputation for producing high-quality oils.

Manufacturer’s Recommendations: It is always best to follow the manufacturer’s recommendations when it comes to choosing the right transmission oil for your Harley 6 Speed. They will know what type of oil is best for your bike.

Following these tips can help you make the right decision when it comes to choosing the best transmission oil for Harley 6 Speed. 

Frequently Asked Questions

How often should I change the transmission fluid for my Harley Davidson?

The frequency of changing the transmission fluid for your Harley Davidson depends on various factors such as riding conditions, usage, and age of the motorcycle. According to the manufacturer’s recommendations, it is recommended to change the transmission fluid every 30,000-60,000 miles or once a year.

What kind of fluid goes in a Harley Davidson tranny?

Harley Davidson should certify the transmission fluid you use on your tranny. As such, you won’t risk voiding your warranty in case of anything. The transmission oil should withstand extreme temperatures and pressure and heavy loading. You can use Red Line 42804 V-Twin transmission oil.

How can I identify the lack of transmission fluid?

The most reliable way to identify a lack of transmission fluid is to check the fluid level on a regular basis. If the fluid level is low or drops below a certain level, it is likely that there is a lack of transmission fluid. If the transmission fluid is dirty or smells burnt, it may indicate that the transmission fluid is low or needs to be changed. Other signs of a lack of transmission fluid include shifting issues, such as slipping or jerking, and an increase in engine noise.

Can I use automatic transmission fluid in my Harley’s primary?

No, you should not use automatic transmission fluid in your Harley’s primary. The primary of a Harley uses a specific type of primary chaincase lubricant that is designed for use in motorcycles. Using the wrong type of lubricant can cause serious damage to your Harley’s primary system.

When should I use a synthetic transmission oil on a Harley 6-Speed?

The best time to use a synthetic transmission oil in a Harley 6-Speed is during an oil change. Synthetic oil offers better protection against wear and tear and can extend the life of the transmission. It is important to make sure you use the correct type of oil for your bike and check with your owner’s manual to make sure you are using the right type of oil for your bike.

Final Thought

If you’re looking for the best transmission oil for Harley 6 speed, one of the oils above is likely a good choice for you. Just be sure to do your research to find the right oil for your bike and your needs, and to follow the manufacturer’s recommendations for changing your transmission oil. Thanks for reading this article.


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