Best Transmission Oil for Harley 6 Speed – 2021 Top 6

Best Transmission Oil for Harley 6 Speed

Whether you realize it yet or not, changing your transmission oil from time to time is vital to ensure your vehicle keeps running smoothly.

This is why it’s extremely important to choose the best oil for the job.

From reducing accumulated engine heat to ensuring optimum engine performance and longevity, there’s a lot a good transmission oil product can do for your Harley Davidson.

Not to mention all the trips to the auto-repair shop you can easily avoid by using the best brands.
If you’re not sure what the best transmission oil for Harley 6 speed is, then you will find this article incredibly useful.

We’ve done all the hard work and have compiled a list of the best models in terms of quality and performance.

If that sounds great to you…then read on.

PictureTransmission OilEditor RatingDetails

Spectro Oil R.HDPG6 Heavy Duty Platinum Synthetic Oil5 StarCheck Price

Maxima Chrome Twin Cam Synthetic Oil4.9 StarCheck Price

ZF LifeGuard Transmission Fluid5 StarCheck Price

RAVENOL J1D2113 ATF Automatic Transmission Fluid5 StarCheck Price

Mobil (112812-4PK) Delvac Synthetic Transmission Fluid4.9 StarCheck Price

Red Line 42804 V-Twin Transmission Oil5 StarCheck Price

Best Transmission Oil for Harley 6 Speed Reviews

After a lot of research, we’ve rounded up the top transmission oil for Harley 6 speed in the market.

1. Spectro Oil R.HDPG6 Heavy Duty Platinum Synthetic Oil

Spectro Oil R.HDPG6 Heavy Duty Platinum Full Synthetic

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To kick-off our list is the Spectro Oil R.HDPG6 Trans Lube. This oil is specifically formulated for Harley riders who cannot blaze the highways without ending up with a noisy 6-speed transmission.

The oil acts as a coolant and helps to optimize the performance of your gear. It was prepared using Spectra’s G4 technology and contains some additives, which help to provide additional protection to your 6-speed transmission by reducing drag and preventing wear.

You will notice a tremendous reduction in gear noise and fifth gear whining. Also, shifting between gears is made a lot smoother while clunks are completely eliminated.

This ultimately leads to a smoother ride and better highway experience. You will be able to cruise for longer times without stressing your engine.

Like most advanced transmission oil, the formula meets every OEM requirements as well as those for Harley bikes.

Overall, this is a high-quality transmission lube that performs really well, even in high load conditions. For its price, it definitely exceeds our expectations.


  • Increased film strength
  • Not affected by heat and heavy load
  • Smoother riding experience
  • Enhanced gear protection


  • A little noisy

2. Maxima Chrome Twin Cam Synthetic Oil

Maxima Racing Oils Chrome 90-119016C Twin Cam Synthetic

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For superior performance that will extend the lifespan of your transmission gear, you cannot go wrong with the Maxima V-Twin Racing Synthetic Oil.

The oil works in all twin-cam engines in Harley Davidson models from 1999 to date. It delivers superior performance to protect your transmission from thermal breakdown and oil deposits.
In other words, when using this formula, you don’t have to worry about your transmission becoming too hot due to long use.

The oil is fully synthetic and has been engineered to serve as a suitable multi-compartment oil for v-twin engines in Harley models. And it’s not just limited to 6-speed gears but also works in 4 and 5-speed transmissions.

It works consistently at all temperatures and will extend the life of your transmission. By using the fluid, you may also notice a significant improvement in shifting, leading to a smoother experience.

The oil also possesses an excellent cooling ability, which helps to prevent overheating and promote a smoother operation.

Overall, you should choose this oil if you want an affordable synthetic solution for your Harley transmission.


  • Excellent lubrication
  • Enhances efficiency
  • Prevents wear
  • Cool operation


  • Expensive

3. ZF LifeGuard Transmission Fluid

Life Guard Fluid 8 (7 Liter) - ZF PARTS

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If you’ve been using transmission oil for a long time, then the chances are that you’ve heard about ZF or come across one of their products.

ZF is a well-known brand that specializes in making complex auto transmissions for different vehicle manufacturers, such as VW, Audi, Mercedes, and BMW. They also make transmission fluids for these gears.

The Lifeguard is one of their best offerings so far. Although this oil is mainly targeted at ZF transmissions, it can also be used for Harley models as long as it’s a 6-speed gear.

It is formulated to boost the performance of your 6-speed transmission while extending its useful life.

The problem with many transmission fluids is that they only perform well at certain temperatures. But this is not so with Lifeguard; you can expect a consistent performance regardless of the weather condition.

One of the major drawbacks of this oil is that it can take a bit of hassle to replace it when doing routine maintenance or repair.

The process is meticulous and maybe a little complicated for some people. This is because you need to carry out at least two successive flushes at specific temperatures.

Overall, this is a high-quality formula that can greatly improve the efficiency of your Harley 6 speed.


  • Very affordable
  • Improves fuel economy
  • Reliable quality
  • Enhances your transmission life


  • Color change may occur sooner

4. RAVENOL J1D2113 ATF Automatic Transmission Fluid

RAVENOL J1D2113 ATF (Automatic Transmission Fluid)

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RAVENOL is another brand known to have some of the best quality transmission oil in the market. The J1D2113 Dual Speed Transmission is one of such offerings.

This formula stands out from so many products in the market in terms of performance and overall value. It is the only product on the list that works for both 6-speed and 8-speed transmission.

So, if you need a formula you can use for another vehicle other than one with a Harley 6-speed transmission, then you will not go wrong with this product. Apart from Harley’s models, you can also use the oil in other vehicle brands such as BMW, Audi, Acura, Honda, Land Rover, and so on.

With a high viscosity index and controlled friction properties, the oil is able to reduce wear in your transmission gear and prevent overheat. This leads to superior performance in both hot and cold weather conditions.

The oil also has an incredibly cooling capacity, which helps to prevent foam formation. It also provides excellent lubrication for the gear components, even at low temperatures.

Like other products on the list, it is resistant to wear and possesses high thermal stability.


  • Corrosion resistance
  • Excellent performance
  • Extends transmission life
  • Reduces wear


  • We couldn’t identify any

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

Mobil (112812-4PK) Delvac Synthetic Transmission Fluid

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Another incredible upgrade you should consider for your Harley 6 Speed is the Delvac Synthetic Transmission Oil by Mobil. It could be the better solution you’ve been searching for to replace your old ATF. You will be amazed by how much quieter and smooth it is.

When it comes to quality and trust, Mobil is one brand that has very few rivals. And this is exactly what the Delvac transmission fluid exemplifies.

The oil is specially formulated to significantly enhance the efficiency of your transmission. It includes artificial base oils and additives that help to that optimize your gear performance and improve shifting in all conditions. This fluid is manufactured to meet the industry’s standards, so you can rely on its ability to deliver.

Furthermore, the oil helps to prevent wearing, which makes the gear synchronizers and bearings to last longer. It also provides exceptional shear stability, which guarantees optimum performance at all temperatures.

You can also expect protection from oxidative and thermal processes, which can hamper engine performance.

To round it up, we believe this fluid is your best bet if you’re looking for a product that will not only improve the efficiency of your Harley 6 speed but also protect the component parts. And the best part is that it works for almost any vehicle.


  • Improved thermal stability
  • Superior gear performance
  • Improves component life
  • Anti-wear


  • A bit pricey

6. Red Line 42804 V-Twin Transmission Oil

Red Line (42804) V-Twin Transmission Car Gear Oil

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Last but definitely not the least among our best transmission oil for Harley 6 speed is the Red Line V-Twin. Widely lauded for its quality and performance, V-Twin is one of the best 6 speed transmission oils in the market today. Apart from Harley bikes, the oil also works for other ATV sports bikes and motocross.

This oil is widely lauded for its anti-wear properties. And much of this is due to its use of additional ingredients such as phosphorus and zinc. These additives basically act as modifiers to reduce friction and wear.

By modifying friction, the oil is able to prevent a high-temperature condition in the transmission gear. Besides prevent overheating, the oil also reduces transmission noise to a great extent. This is why it’s commonly regarded as being shockproof.

The oil also does a good job of clearing out shifting clunks while enhancing shifting operation.
Finally, we have no doubt that using this formula will lead to a significant improvement in your 6 speed transmission and overall bike performance.


  • Reduced wear and tear
  • Shockproof
  • Enhances shifting operation
  • Improved bike performance


  • A little noisy

What Is 6 Speed Transmission Oil?

If you’re using any one of the latest Harley bikes, then you’ve probably found the extra gear to be very useful in a number of situations.

The greatest advantage of using 6 Speed Transmission is that it helps you overcome the lethargic acceleration pitfalls common with 5 Speed and lower gears.

In other words, you can cruise the local freeways for long hours without worrying about stressing the engine. But most of the time, this is hardly the case with the Harley Davidson.

This is because unlike water-cooled bikes, Harley relies on air for cooling, and so gets hot quickly when moving at higher speeds. Luckily, the transmission exists to solve this problem.

The transmission oil is basically a fluid that is used to lubricate the components of a 6-speed transmission to maintain optimal temperature even when the motorcycle is moving at a higher speed for a long time.

Using the right oil will ensure your bike runs smoothly even in high speed or load conditions without extreme vibration or noise.

This is possible because the oil basically acts as a coolant and thus is not affected by extreme heat during long drives.

Features to Consider Before Buying

In order to get a transmission fluid that will not disappoint, there are some key things you need to look out for before making your final decision. Let’s quickly look at them.

Natural vs. Synthetic

Depending on your needs, you can decide to choose between two types of transmission oil – natural or synthetic. While natural oil is very popular, the most preferred choice is synthetic oil.

Synthetic transmission oil generally performs better than natural options due to their improved resistance to various conditions in the transmission gear. This includes heat, oxidation, and sheer.

You will also get more use from a synthetic formula than organic-based oil. However, natural oil is usually more eco-friendly.


In addition to the type of oil, you also want to consider its viscosity.

Using a product that doesn’t have the required viscosity of your vehicle can cause your 6-speed transmission to fail.

So, make sure the oil viscosity meets your vehicle’s requirement before putting out your money for the product.


It is important not to compromise quality when shopping for anything of use, especially when it has to do with your motorcycle. And it is better to go for brands with proven credibility regardless of their popularity.

Avoid ridiculously cheap products as they will likely end up disappointing you. Quality should always come before price.


Another thing to look out for when looking for a fluid replacement is the fluid type. This is important because it can affect the life of your Harley transmission. The fluid type also gives you an idea of its performance level.

It is extremely important you choose a product that is compatible with your bike.
So, make sure you check your Harley specifications and recommendations. You should be able to find this in the owner’s manual.

Final Words

Regardless of the type of transmission, you have in your vehicle, using a good transmission fluid is extremely important if you don’t want to have problems when shifting gears.

Luckily, with our review of the best transmission oil for Harley 6 speed, you shouldn’t have any difficulty finding the perfect product for your gear.

Please let us know if you have any more questions. Or else we want to hear about your experience using any one of the items above.

Resources & References


Hi, I’m Adam Vachon, an avid learner and working in the product marketing niche for the last few years. The problem I faced when marketing products for manufacturers made me interested in starting GearsLoft.

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