OIL IS ALWAYS CHEAPER THAN STEEL
The Great Synthetic Oil Myth
by Fritz Guenther #22T
 As an avid dirt bike enthusiast I own several vintage and more than several modern bikes, both 2 strokes and 4. It never ceases to amaze me how many times I’ve heard riders at the track or on the net say:
“Never run synthetic oil because it will ruin your clutch” and/or “My mechanic told me synthetic oil will cause your clutch to slip”
My real job as a lubrication analyst/specialist for a major oil company has allowed me to understand through science that synthetic lubricants are probably better suited for dirt bikes than any other application. I’m sure there are some readers who will tell me an F1, top fuel or gas turbine engine is tougher on lubrication than a dirt bike. You’ll get no argument from me but how many of us have an F1, top fuel or a gas turbine in our garage?
Care to guess when the first synthetic oils were produced from hydrocarbon molecules? Would you believe 1877? No it’s not a typo, due to lack of demand it wasn’t until the early 1970’s that a commercial demand started driving the production of synthetics. It was fully 100 years later, in the middle to late 1980’s that synthetic lubricants really came into their own and began to be widely accepted by the public.*
Mineral based “Dino” oils have reached their pinnacle of development, in other words we’re making it about as good as we can and it aint gonna get no better. Sure we can blend in new, better and more effective additives, or even add a pinch synthetic base stock, ever heard of semi-synthetics? Bottom line is lubricant base stock refined from crude oil is probably as good as it’s going to get. Has engine development reached its design peak as well? Don’t think so, everyone wants higher, hotter, faster, lighter, more powerful “stuff”
To find out what makes 100% synthetic lubricants better than mineral based oils we must first understand what we are asking a lubricant to do. Some of the lab rats like to throw around big words like hydrodynamic fluid film and elasto-hydrodynamic fluid to mention a few. This is just a fancy way to say a lubricant is there to keep 2 surfaces from coming into contact with each other. When you put 2 metal surfaces in contact with each other under extreme heat and pressure without a barrier between them you end up with what is known as adhesive wear or more commonly called seizing, spalling, scoring, and pitting. Yes, lubricants also serve to cool the engine and carry away the heat but that is not their primary function, after all water is a pretty effective heat transfer medium but not very effective at preventing adhesive wear. Which brings us to viscosity?
Ladies and Gents this is what it’s all about, you can take all the other fancy 9 syllable words and forget about them. Viscosity is what lubrication is all about, period. Not enough viscosity and you have metal on metal leading to adhesive wear, too much viscosity and your lubricant isn’t going to go where it’s needed, again leading to adhesive wear and damage. Your engine manufacturer and more specifically the engineers that designed the bearings and gears in your engine specify a lubricant viscosity for a given operating temperature. Whether you use a mineral, semi-synthetic or 100% synthetic oil the best advice I can give you is to stick with manufacturers recommended viscosity.
The properties of mineral oil base stocks are largely dependant on the location the crude came from. Whether paraffinic or naphthalenic the crude feed stock will yield a lubricant with a different molecular structure and properties. Mother Nature didn’t do a bad job it’s just that man and science did her one better. Synthetic base stocks (of which 80% are PAO or polyalfaolifin) are man made by chemically combining small molecules to form larger molecules that are identical in every way. The end result is a fluid that has very predictable and repeatable properties; it’s the designer drug of the lubrication world if you will.
The end result is that 100% synthetic lubricants flow better at lower temperatures have a much higher thermal stability, meaning it doesn’t degrade or thicken at higher temperatures due to the lighter molecules “flashing off” and has better oxidation stability which means it’s going to perform it’s designed function longer than mineral based oils to name a few. Think of the conditions we subject our bikes to every time we ride or race; high RPM, slamming gears, feathering the clutch, riding in dirt, mud, water, think our engines could benefit from a better lubricant? Yep!
Now that I’ve hopefully got you considering the benefits of synthetic lubricants here are some things to keep in mind. If you use a 100% synthetic oil that is motorcycle specific it will not contain additives in high enough quantities to cause clutch slippage problems. If you don’t like paying the high price of 100% synthetic motorcycle oil and plan to use less expensive automobile synthetic oil you need to be selective. Some of the newer synthetic automobile oils carry the EC rating which means they are “energy conserving” oils and may contain high enough amounts of the additive Molybdenum Disulfide or “moly” which is a solid metal that has proven to be an excellent friction reducer but in high enough concentrations can cause clutch slippage. The 100% synthetic automobile oil I’ve used (which is NOT made by the company I work for) in my bikes for years typically has between 90 and 100 parts per million of moly and I’ve never had a clutch problem. At what levels does moly cause a clutch problem? Don’t know, I’ve never actually come across a rider that had a clutch problem caused by synthetic oil.
In closing, please don’t pass up the opportunity to give your bike the best oil you can just because of a wives tale about synthetic lubricants. Don’t be afraid to learn something new, do some research on your own. Maybe even send a few samples to the lab to see what’s in your oil. No matter what lubricant you choose to run if you keep it clean, cool and dry you’ll be rewarded with increased reliability.
* Synthetic Lubricants and High-Performance Functional Fluids by Rudnik and Shubkin, 1999
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