Harley Davidson Syn3 Oil - A True Synthetic or Not?

Motorcycle Lubrication White Paper

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Does your brand new Harley Davidson motorcycle "use" a lot of oil (1/2 quart or so every 1,000 miles)? Here's what you need to know about volatility and poor quality motor oils...


The oil's tendency to burn off at high temperatures is controlled by the base oil's chemical makeup. Base oils that contain volatile light fractions of oils will evaporate more readily when exposed to high temperatures. Base oils with less light fractions, or light fractions that are not as volatile, will not be as susceptible to burn off . Low-quality engine oils that contain high concentrations of volatile light fractions can contribute to a vehicle "using" a lot of oil as it evaporates during operation. The oil's flash point, the point at which it will spontaneously ignite when subjected to high heat, is also dependent upon the base oil's volatility characteristics.

A brand new motor or a motor that is in good mechanical condition with no leaks should not "use" oil. If your motorcycle is "using" oil for no apparent reason, a likely cause could be the oil [quality] itself. A simple test would be to replace the factory fill SYN3 or HD360 with something else (better) and see if the condition goes away. If you quit having to top off your oil every few hundred miles, then you have your answer.

Federal law prohibits any company, including Harley Davidson, from voiding your warranty if you use something other than Harley Davidson branded lubricants. You will DEFINITELY notice the difference about ten seconds after you ride off with Amsoil in your bike. Your motor will run smoother, quieter and cooler. Your transmission will shift a LOT easier. And your chaincase will be much more quiet. And after a thousand miles of riding, you'll notice that you DON'T have to add 1/2 quart of oil in between oil changes because Amsoil is a LOT less volatile.


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NOTE: Severe gear oil is not recommended for Twin Cam Harley Davidson Transmissions.
Actually, it's NEVER been recommended but it was very popular with old school Bikers
such as myself in Evolution and Shovelhead Harleys. According to AMSOIL, there are
additives in severe gear lubricants that can be harmful to brass. Severe gear oils
are formulated for hypoid gear assemblies and Harley transmissions do not use hypoid
gears. That said, I used it for decades and never had a problem with it. However,
you will DEFINITELT notice the improvement if you replace your syn3 tranny fluid
with AMSOIL 20W-50. And you will DEFINITELY notice the improvement if you replace
AMSOIL 20W-50 with AMSOIL V-Twin transmission fluid!

Harley Davidson advertising states that "SYN3 oil is a proprietary blend created specifically for Harley Davidson motors, transmissions and primary chaincases". The VERY strong implication in their advertising is that SYN3 is the only appropriate lubricant for Harley Davidson motorcycles. Their advertising gives the VERY strong impression that using anything other than a Harley Davidson brand lubricant in their motorcycles will cause reliability problems, component damage and warranty claim problems.

This (strongly discouraging the use of non-manufacturer's branded oil) is a marketing strategy that has become popular in recent years, especially with European auto manufacturers. Most vehicle owners don't know that much about lubrication to begin with. And few want to take a chance of getting mired up in a warranty service denial judgment by Dealerships who live to cheat customers out of legitimate warranty claim services. So, most owners opt to "play it safe" and comply with these deceitful manufacturer's edicts, as bogus and as legally unenforceable as they are. However, in Harley Davidson's case, the claim that using someone else's 100% synthetic increases the risk of damaging your motor may have more than a little credibility... but not for the reasons you might think. It may not be so much that SYN3 is a wonderful high quality lubricant so much as design problems with air cooled motors such as Harley Davidson's (although air cooled metrics do not seem to have these problems). Note the "synthetic lubricants cause bearing skid problems in Harley Davidson motorcycles" information that is provided by Harley Davidson themselves. The bearing skid information below was taken directly off of the official Harley Davidson web site.

Harley Davidson does not even put a service class or API/JASO rating on their oil containers. One could correctly wonder if this is because the product is mediocre or perhaps even inferior as compared to products like Amsoil, Redline, Mobil-1 and so on... if SYN3 was such a very high quality oil, as Harley Davidson claims, one would think that the packaging would proudly proclaim that SYN3 is JASO MA2 rated... which is as good as it gets. Consumers would be wise to be skeptical about any product that claims to be wonderful but refuses to disclose what's in it.

Fortunately, businesses can play "I've got a secret" with the public but not with the US Government. Lubricants are required to have a Material Data Sheet on file that states all of the materials that are present in any product of this type. Let's see what the SYN3 sheet looks like.

According to the "Material Safety Data Sheet" for H-D's SYN3, it is chemically a blend of 60% synthetic and 40% petroleum oils.

This is not illegal but it's certainly deceptive. The Courts have ruled that it is legal to advertise a product that has a chemical composition that includes at least SOME synthetic properties as a "synthetic lubricant".. in the case of SYN3, that oil is a 60/40 blend and not a true, 100% synthetic or anything even close to it.

Material Safety Data Sheet (MSDS) on the SYN-3, as filed with the Federal Government.
Manufactured by - Citgo Petroleum.

Composition section:


(1) 1-Decene Homopolymer, hydrogenated
50% - 70%

(2) Proprietary Ingredients
Proprietary Mixture
1% - 10%

(3) Polyisobutylene
1% - 10%

(4) Distillates, Petroleum, Hydrotreated Heavy Paraffinic
0% - 20%

(5) Distillates, Petroleum, Solvent-Refined Heavy Paraffinic
0% - 20%

(6) Zinc Alkyldithiophosphate
0% - 2%


Item (1) is a Group IV base oil. unable to locate the manufacturer of this base oil. Group IV and V base oils are the only "true" synthetics to the cognoscenti.

Item (2) is probably their additive package (boron, calcium, magnesium, phosphorous, moly), but it is conceivable there could also be some "secret" synthetic oil, maybe an ester type oil, included in it.

Item (3) is a fancy name for synthetic rubber (or elastomer) but this is probably considered to be "synthetic" oil as well.

Item (4) is a Group II base oil, namely Conoco Pure Performance Base Oil, either 110N, 225N or 600N. Pretty much no one is calling a Group II oil a synthetic.

Item (5), No specific information on this group but it is Conoco's Cit-Con 650N Base Oil. It's presumed that it is a Group I oil as it is solvent refined. Most quality blenders are not using Group I oils in their premium motor oils and they are not considered synthetics.

(From the MSDS for the HD 360 20w50 oil: The major base oil constituents in it are the same ones as are listed in Items (4) & (5) above.) H-D 360 is marketed as a non-synthetic, conventional (petroleum-based) lubricant.

Items (4) & (5) above, are likely needed to keep the old air-heads running without bearing skid and gasket leaks. This design flaw is clearly stated on Harley Davidson's own web site.

Items (4) and (5) are particularly interesting to me since Harley Davidson's own marketing information makes reference to how SYN3 is formulated to prevent bearing skid. Are they using petroleum-based ingredients to compensate for basic design flaws in their motorcycles? For decades, Harley Davidson has strongly discouraged the use of synthetic lubricants in their motorcycles. Could this be why and could running a 100% synthetic in a Harley Davidson still be problematic?

As for gasket/seal/o-ring leak prevention.... running thick as molasses straight SAE 50 and even SAE 60 has been the common "remedy" to actually replacing worn gaskets, seals and o-rings. Since even at warm temperatures, these thick viscosities provide virtually no lubrication at start up. This "sub-optimal" lubrication continues for several minutes until the oil approaches something close to 212 degrees F. I have always considered the use on these lubricants to be ill-advised in ANY motor.

Harley-Davidson characterizes SYN3 in their advertising as:
"Developed with a proprietary blend of three synthetic basestocks, ..."

Since there are significant amounts of Group I and II oils in the SYN3, could the MoCo have stretched the definition of "synthetic" a bit further than Castrol did when changing Syntec from a PAO Group IV base to a hydrocracked Group III base?

Exxon/Mobil (Mobil 1 synthetic) lost a lawsuit trying to go after a few oil companies for advertising blends as full synthetic. Mobil lost. Consequently, the oil companies do not have to disclose on the label it contains Group I, II or III base stocks which are all petroleum based.

Therefore, it is certainly legal if not factually correct for Harley Davidson to market SYN3 as a full synthetic, even though it is only 60% synthetic with the remaining content being petroleum based. But in reality, SYN3 is more of a semi-synthetic. IMHO Harley Davidson ought to be more forthcoming about that fact rather than giving customers the false impression that SYN3 is a 100% synthetic lubricant which it CLEARLY is not.

If you want a fully synthetic oil, Mobil-1, RedLine or Amsoil might be better choices. However, Harley Davidson's own disclosure about bearing skid problems may mean that running a full synthetic in a Harley Davidson might be ill-advised.

From the official Harley Davidson web site:

What are the key benefits to using SYN3? SYN3 Lubricant:
  • Can be used in the engine, primary chaincase, and transmission.
  • Offers improved film strength for superior wear protection at high temperature, and improved deposit control for a cleaner engine, transmission, and primary chaincase.
  • Is formulated for reduced oil consumption, improved wear protection, high temperature detergency, and superior overall field performance.
  • Provides high temperature film strength, which means the lubricant maintains film thickness in high power output and high engine speed conditions, keeping the metal parts from rubbing against each other and resulting in less wear.
In the past, Harley-Davidson® did not recommend the use of synthetic oils in H-D/Buell® motorcycles. Why is H-D introducing a synthetic now? Because Harley-Davidson cannot test and certify all available synthetics on the market nor control their oil and additive formulations, we have discouraged their use. However, Harley-Davidson, in close partnership with our suppliers, analyzed available petrochemical technology and developed a custom-blended candidate fluid that can be used in all three cavities of a Harley-Davidson/Buell motorcycle. This product has been exclusively designed for Harley-Davidson and is the only synthetic product TESTED and CERTIFIED by Harley-Davidson engineering for use in H-D/Buell motorcycles.
What kind of testing was done on SYN3? Over three years of laboratory bench testing, dynamometer testing under accelerated conditions, open road vehicle durability testing, closed course durability testing, and wear and deposit rating analysis was conducted on SYN3.
Who makes or blends this product? SYN3 is a proprietary blend, exclusively custom-blended for Harley-Davidson.
Will H-D 360 Motorcycle Oil be replaced by SYN3? Harley-Davidson continues to offer H-D 360 Motorcycle Oil. SYN3 is an alternative lubricant product from Harley-Davidson, and in particular, a formula that is very effective for high performance engines and hot climate applications.
In which motorcycle models can SYN3 be used? SYN3 is formulated for use in Harley-Davidson Evolution® XL, Evolution 1340, Twin Cam® (all displacements) and Revolution-equipped models and all Buell® models.
Can SYN3 be used in ShovelheadTM engines, 4-speed Big Twin transmissions, and early Shovelhead 5-speed transmissions? Harley-Davidson did not test SYN3 in these engine configurations. There are a multitude of tests that must be completed before a lubricant can be certified for use in Harley-Davidson engines, primary chaincases and transmissions. Many of these tests require that the components be brand new, and the required quantity of new powertrains for testing and validation could not be procured.
Will the use of SYN3 lengthen my service intervals? No, we recommend that you still follow your owner's manual for the proper service schedule for your vehicle.
If this product is a high performance lubricant, why would my service intervals not be extended? While SYN3 will help reduce the amount of impurities to your engine, no lubricant product can reduce fuel dilution (this happens every time you start your vehicle). As a result, the regular service schedule is recommended for optimum performance of your vehicle.

Lubricants begin to break down the moment the engine is started. The long molecular strands of the lubricant begin to be sheared between the faces of gears, pistons or other moving parts. SYN3 was tested to confirm that the lubricant provides the protection required for the engine, primary chaincase and transmission for the drain intervals specified in the Owner's Manual.

A common concern with other available synthetic oils is that roller bearings may "skate" or "float" in the bearing race, and not actually rotate as designed. How does SYN3 prevent this from happening? SYN3 was formulated to provide improved high temperature stability, shear stability, proper lubricity for anti-wear (without roller bearing "skate" or "float") and maintain the coefficient of friction for proper clutch operation (without clutch slippage).

Harley-Davidson does not recommend any lubricants that have not been tested and approved by Harley-Davidson engineering because we do not control the formulations. Lubricants are reformulated frequently to meet changing American Petroleum Institute (API) Ratings. API Ratings are developed and tested for use in water-cooled automotive engines and diesel applications. There is no API Rating (classification) for Motorcycle Engines.

Harley-Davidson, in close partnership with our suppliers, analyzed available petrochemical technology and developed a custom-blended candidate fluid that could be used in all three cavities of a Harley-Davidson/Buell motorcycle.

Can a brand new bike have its fluids drained and refilled with SYN3, without voiding the warranty? Yes, this product can be used as a first fill upon delivery of a new motorcycle. The formula is approved by Harley-Davidson for use in all stages of engine life and is not detrimental to the engine break-in cycle.
Do the cavities that are going to be filled with SYN3 need to be completely drained? Yes, the cavities that are to be filled with SYN3 must be completely drained. It is not recommended to mix SYN3 with other lubricant products. During servicing, a residual amount of fluid will remain in the sumps. It is not required to "flush" out the residual fluids.
Should I put a can of additive in with each oil change? No, SYN3 is blended with an additive package already included. Other additives are not needed and may not be compatible with SYN3. In fact, oil additives may actually dilute the SYN3 formulation.
If I'm on the road, and realize I'm down a quart of engine oil, and cannot buy SYN3, what should I use? If SYN3 is not available and addition of motor oil is required, the first choice would be to add H-D 360 SAE 20W50 to the SYN3 for engine lubrication. Although H-D 360 is compatible with SYN3, we suggest the mixture of the fluids be changed as soon as possible. If H-D 360 is not available, the second choice would be to add an acceptable diesel engine oil as listed in the Owner's Manual, and again we suggest the mixture of the fluids be changed as soon as possible. DO NOT add diesel engine oil to the primary chaincase or transmission.
Can a quart of oil be added to the Primary Chaincase or Transmission when SYN3 is not available? If SYN3 is not available and addition of lubricant to the Primary Chaincase (Evolution 1340 and Twin Cam 88) is required, the first choice would be to add H-D Primary Chaincase Lubricant. Although H-D Primary Chaincase Lubricant is compatible with SYN3, we suggest the mixture of the fluids be changed as soon as possible.

If SYN3 is not available and addition of lubricant to the Primary Chaincase and Transmission (common reservoir) for Evolution XL and all Buell models is required, the first choice would be to add H-D Sport-Trans Fluid. Although H-D Sport-Trans Fluid is compatible with SYN3, we suggest the mixture of the fluids be changed as soon as possible.

If SYN3 is not available and addition of lubricant to the Transmission (Evolution 1340 andTwin Cam 88) is required, DO NOT ADD H-D Semi-Synthetic Transmission Lubricant as the two lubricants are NOT compatible.

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