With so much discussion of late about synthetic oil vs. dyno oil, I thought it would be a good subject to look into. Who knows, I might learn something new and even change my mind. Stranger things have happened.

Most of you know my thoughts on synthetic oils. If you don’t, I’ll be right up front and say, I’m not a fan, I prefer a good dyno oil. It has nothing to do with the quality of synthetics; it’s basically all about cost. The only performance question I have with synthetics is the effect it has on our clutch. With this minor disclaimer, I promise to be as objective as possible.

Considering what we hear about the synthetic effect on a wet clutch, I thought it best to understand the motorcycle clutch before we look at oil. We all know the purpose of a clutch so I don’t think we need to start there, how about we start with the purpose of or the reason behind a wet clutch?  

Proper clutch operation giving you a smooth transfer of power from the engine to the wheels requires friction. Also, the motorcycle clutch spends a lot of time in the “Friction Zone” with our slow speed maneuvers. Friction is heat and heat is an enemy of your clutch. To control the heat, the clutch is immersed in oil. The same oil that lubes and protects your engine also surrounds your clutch and that’s the rub or lack thereof. The clutch requires friction to operate; it doesn’t work with lubrication or the additives. The purpose of the oil on a wet clutch is to cool, not to lubricate.

Oil not classified or specified for a wet clutch and containing improper additives  can be too slick, eliminating the needed friction causing your clutch to slip, glaze and ultimately need replacing before its time. This alone, is a good reason to run a motorcycle rated or approved oil.

After reading a few articles I find motorcycle specific oil typically has a higher level of detergents, and anti-wear additives like zinc and phosphorus. These additives are important in protecting high RPM engines from wear. I also found that automotive manufacturers are requesting these additives be left out of automotive oil. The reason is their extended warranties on the emission systems, (some as long as 10 years / 150,000 miles) claiming that high concentrations of these additives are contaminating their catalytic converters, effecting emissions and ultimately costing the automotive manufactures money. Some motorcycles have a catalytic converter and they will experience the same issues of the auto. The difference is the length of the warranty period. In other words, the motorcycle will no longer be under warranty and the cost is ours, not the manufacturer.

I also read that automotive oils are adding friction modifiers to reduce additional friction trying to offset some of the lost fuel economy from the Governments mandated mixed fuels such as ethanol. I could list these additives and explain their purpose but it would add too much length to the article and chances are, it would just confuse the issue and muddy the water. If you're interested, check out the reference material links below or run your own Google search. There is more information on this subject than you can imagine. 

The more I read, the more it makes the case that specific applications require different additives and the new automotive oils can reduce friction causing the wet clutch to slip.

So what classification do we need for our motorcycle with a wet clutch? Bottom line, your owner’s manual should tell you. We are all familiar with the API rating of oil and we should stay within those guidelines. Any outdated classification is superseded or covered under a newer classification.

Now under the “learn something new everyday” category, I had no idea there was another classification to consider. The Japanese Automotive Standards Organization or JASO is the only organization to test oils for a motorcycle with a wet clutch. They have two classifications, JASO-MA and JASO-MB. The MA classification has NO friction modifiers added and the MB classification HAS friction modifiers added. If you use a JASO-MA classified oil you are guaranteed not to have problems with your clutch. If you have an API rating, try to match that as well as the JASO-MA.

I always thought synthetic oil was slicker than dyno oil due to the manufacturing process and standard additives. I learned this is not the case. The main difference with synthetic oil is that its molecular structure is more uniform which reduces resistance or friction and heat better than an irregular shape and size of dyno oil. I'm guessing this is also why we notice a better shifting transmission with synthetics.

Something I must concede after my research, it’s completely safe and acceptable to run certain synthetic oils in a motorcycle with a wet clutch, depending on the type or classification of that oil. In other words, not all synthetics are created equal. Some synthetic oils have wear inhibitors added that may not be acceptable but with some research you can find an acceptable synthetic option. I’m sure there are several options available but the only synthetic I found to specifically address motorcycle use and the wet clutch issue was Amsoil. If you Google wet clutches and synthetic oil you will be amazed at how much information is available from Amsoil on the subject.

Now that we’ve answered the wet clutch concern it’s time to look at price.

For the price comparison I thought I would use Honda GN4 dyno oil, the new Honda synthetic oil and because Canon Sue sells Amsoil and it will work for our bikes, I’ll use it as a second synthetic option.

     Dyno Oil
     Honda GN4 - $4.58 per quart
    Honda oil filter – $8.99 each
    Total oil change price - $27.31

      Synthetic Oil
     Honda Synthetic HP4S - $7.91 per quart
    Honda oil filter – $8.99 each
    Total oil change price - $40.63
 

     Synthetic Oil
     Amsoil Synthetic - $10.95 per quart
    Amsoil oil filter - $16.10 each
    Total oil change price - $59.90

The Honda owners manual suggests with normal operation to change your oil every 7500 miles. Most people believe this to be too long, changing their oil around 5K miles and that’s what we’ll use for this purpose. Amsoil suggests for 4 stroke motorcycle engines to change the oil at 2 times the OEM suggested interval or one year whichever comes first.

For the purposes of this cost comparison I’m going to assume we ride 10K miles per year.

     Dyno Oil                                                                       
     Honda GN4
    Two oil changes - total yearly cost $54.62 
    10K miles ridden – CPM 0.0055

     Synthetic Oil
     Honda Synthetic HP4S
    One oil change - total yearly cost $40.63
    10K miles ridden – CPM 0.0041

     Synthetic Oil
     Amsoil Synthetic
    One oil change - total cost $59.60
    10K miles ridden – CPM 0.0060

Putting this to paper and seeing how close the cost of synthetic is to dyno oil surprises me. However this is using an estimated 10K miles so please keep in mind, any less than a 10K mile oil change or less than 10K miles per year and having to change your synthetic oil prematurely the cost will dramatically increase. With half those miles (5K) dyno drops to a cost of $27.31 with a CPM of 0.0030 and your synthetic price will stay the same.

To estimate your actual yearly cost or cost per mile (CPM) use your own average miles ridden per year.

In conclusion: With additives, such as wear inhibitors and friction reducers commonly added to dyno as well as synthetic oils, I would suggest an oil specified for motorcycle use. Look for the JASO-MA rating as well as the API rating.

Synthetic oil can be a cost effective option as long as you ride 10K miles or more per year.

I hope this information is helpful. Bottom line, it's up to you to decide if dyno oil or synthetic oil is a better choice for your use, just be sure to use motorcycle rated oils.

Additional information coming soon: Oil change intervals have been a topic of discussion and much confusion. I have heard some people change their oil as early as 2K miles and others go as long as 10K miles. With new cleaner running engines and the better refinement techniques of oil, we know the 3K miles or 30 days oil change interval is outdated. To help determine the effectiveness of oil at higher mileages, I am currently compiling information to help answer this question.

Several of us have contacted Blackstone Laboratories and we're having them check our various oils at various change intervals. Once we get enough of these samples examined to form a trend, we'll share that information to help clear up this issue. If you're interested in helping with this, contact Blackstone linked below and send me a copy of your oil analysis.

If you have any questions or comments on either of these subjects, send them my way. I’d be glad to hear what you think.

Until we ride again...

Credits and reference links: (Websites are linked within name or title in a new window)
Amsoil Prices from Canon Sue's website, Amsoil - Product Recommendation and Drain Interval Chart PDF, Amsoil Synthetics, Slipperiness and Wet Clutches, Amsoil Tech Services Bulletin PDF, Blackstone Laboratories Motorcycle oil analysis, Honda oil prices and oil pictures taken form Honda Direct Line, The Melting Pot - A collection of thoughts and ideas, Smartsynthetics.com Motorcycle Oil Technicle Facts, Exploded view of the VTX clutch from the Honda parts fiche on Sun Enterprises website, V Twin Cafe' Motorcycle Performance Guide