By: By: Richard Sheraga
Breaking in my new motorcycle engine. Should I use synthethic oil or conventional oil?
The commonplace opinion is that engine breaking should be completed using only conventional oil as synthetic oil "is too slippery" and wont actually allow the internal parts to set and seal. THIS IS NOT TRUE!!
Ok, first of all, lets 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 1920s, you were doing good to not need an engine rebuild after 3000 miles. In the 1960s, a Trimph 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 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 was 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 essense there is no wear. Its 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 results 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?
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.
