Breaking in my new motorcycle engine. Should I use synthetic oil or conventional oil?
The commonplace opinion is that engine break-in should be completed using only conventional oil as synthetic oil "is too slippery" and won't actually allow the internal parts to set and seal. THIS IS NOT TRUE!!
Ok, first of all, let's think about the motorcycle now in relation to earlier years. The quality and materials are better. No doubt about it. The materials used in engines of today are much more durable then say the materials used in early year Triumphs, Nortons, Harleys, or even Hondas for that matter. In the 1920's, you were doing good to not need an engine rebuild after 3000 miles. In the 1960's, a Triumph or BSA needed new valves, rings, and general top end work at about 25,000 miles. A typical Honda Hawk of that vintage could go 50,000 miles between ring jobs, which very well might have led to the demise of some of the British motorcycles over time. Now, some of the modern engines can literally go 150,000 miles and more. Just ask some of your Goldwing riders.
Years ago, the fit and finish of a motor was not nearly as smooth as it is now. We can thank technology for that. Break-in is the process of wearing away the little rough spots; bumps, protrusions, and excess bits of metal that stick out between the moving parts. The whole purpose of a proper break-in is to minimize the damage caused due to the rubbing together of these rough spots between the piston and the cylinder.
If there is perfect lubrication between the moving surfaces, in essence there is no wear. It's when we have oil breakdown that the film of oil that seperates the moving parts allows for contact and then galling, piston seizure and terrible damage in more severe cases.
The two (2) oil properties that are needed to avoid this damage and destruction are: film strength and temperature stability.
Petroleum oil has about 250,000 psi film strength and can withstand temperature up to about 300 degrees F.
Synthetic oil has about 500,000 psi film strenth and can withstand temperatures to about 500 degrees F. Which would you prefer if you were the engine?
Synthentic oils do not prevent or greatly extend break-in time. They do reduce or eliminate the damage that might take place between mismatched parts. Those bits and pieces that protrude still wear in but they do it more gently with the extra protection afforded by synthetic oils.
Many people have asked me what oil I spefically use. I tend to use a "DIESEL" synthetic. Why you ask? Contrary to popular belief, a "diesel" synthetic is not diesel specific. It can be used in a diesel or conventional gasoline internal combustion engine. However, it is better at trapping particulates and contamination than a non-diesel synthetic oil. I tend to use Rotella Synthetic, a product produced by Shell Oil. So now you know. In no way am I endorsing or promoting this particular product...use what you are comfortable with.
SYNTHETIC OIL IS THE BEST WAY TO GET THE BEST BREAK-IN AND OVERALL ENGINE LIFE OF YOUR MOTORCYCLE IN THIS WRITER'S OPINION