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Synthetic for break in?
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Posted by: Jaybird
I see many folks subscribing to the theory that a synthetic oil is "too slippery" to use for break in. My first thought is that people simply don't understand what is happening with lubrication.
There are two relms of lubrication that are of concern in our motors. Full Fluid Film, and Boundery type lubrication.
Fluid film lubrication is the discription of what motor oil does. It provides a film between the moving metal friction surfaces. This film actually seperates the two metal surfaces and does not allow them to touch. The result is no breaking off of the little peaks that are seen in the metal at the microscopic level. Both conventional dino oil and synthetic do the very same thing as far as fluid film protection of the surfaces.
Once conditions exist that allow these little microscopic peaks to violate and break through the oil film, there needs to be added protection that the oil (either dino or syn) cannot handle. So, mfgs add additional lubrication products to the oil that will either fill in the little valleys of the metal surface, or they will be chem-absorbed into the oxide layer of the metal. The result will protect the metal surfaces even when the peaks touch one another after the oil film has failed.
These products are often refered to as "friction modifiers". I know that this term scares many folks, but it is mostly due to them not totally understanding what they are or how they work.
There are friction modifiers in ALL motor oils, either dino or synthetic.
Some oils simply carry more of one type or another that would classify them as "energy conserving" oil.
To hurry my point along...both dino and synthetic oils only protect to a certain point, they then must depend on other additives to protect. And when we rebuild a motor, there will be some mis-match going on with the rings and cylinder wall that means that there may well be some excessive wear of the ring or wall during start-up and break in, but the choice of oil type does not effect this one bit. Infact, using an oil that has very little additives in the package could result in the "seating" to be more wear than is needed.
Yes, synthetic oil has better shear strength than dino oil, and it also provides protection at higher heats than conventional oils will, but the relm of wear that we are concerned with during "ring seat" has little to do with the fluid film protection of the oil.
As I stated above, it is boundery lubrication that we are concerned with here. So, you can either depend on the additives in the oil to do the protection for you OR you can use a break in fluid while the parts are disassembled. Break in fluids are basically friction modifying products in concentrated form. Some are nothing more than molybdenum, which makes for a fantastic boundery protector for break-in, but there may be issues with certain wet clutches that make moly not the best choice for our sports rebuilds.
Other types of rebuild fluid are actually a chemical that is absorbed into the oxide layer of the metal surface, and when the two surfaces break through the fluid film, they will acutually allow the peaks and craters of the metal to bend away from each other, rather than shear off. What this does is allow the metal to "seat" while keeping the wear during this process to a minimum.
Like I've said, most oils contain these type of products, however during the critical time of a new rebuild, a concentration of these fluids is warranted.
Bottom line:
Synthetic oil will not act any differently than conventional dino oil during break-in. It is the additives in the oil package or the break-in fluid that you coat the surfaces with that can make a difference.<!-- / message --><!-- sig -->
Posted by: JTT
I find this very interesting, but have a very rudementary understanding of lubrication so please bare with me if I sound dumb here...
Just for clarification in my own head Jay, so you are saying that the "friction modifiers" are the "boundary" protection, correct?
I'm not familiar with these "break in fluids" or how you would use them in practice, could you elaborate for me please?
Also, how do we, as consumers, know what additive packages the oil manufacturers are actually using and how it effects our application?
Posted by: Jaybird
Yes, friction modifiers are in lubricants to provide protection at the boundery lubrication relm. Most often they are long-chain molecular structured additives. Other products used are actually lubricating solids such as zinc or moly.
When you rebuild your motor, it is always a good idea to coat everything manually with a break-in fluid. Some only use motor oil or two stroke oil, but there are fluids that are much more suited for this. The mis-match of parts during start-up and during the first few heat-cool cylces demands that some sort of lubrication product, over and above the oil in the sump or the pre-mix, be available.
Most all oil mfg's use products that are propriatory. Which means they won't tell you what they are.
Trial and error, or anecdotal info from others is about the best you can do.
Some items will be listed by the mfg, such as zinc-d or moly. A very high moly content fluid (over 300ppm) may actually cause some clutches to slip a bit.
Lots of oils have reformulated to lessen or remove zinc completely, as it seems to foul catalytic coverters on autos.
You can usually feel sucure with a moto specific fluid, but at a high cost. There are fluids that are plenty suitible for far less money, but you wil need to find out what suits your ride best if you want to use a less expensive fluid.
The lack of the "Energy Conserving" rating of an oil has proven to be a good indicator of a fluid that won't cause clutch problems. Also, it is known that full synthetic fluids can withstand a higher running temp than conventional organic oils.
Posted by: Faded
Jay, good info, thanks. 
There is an oil site, HERE, that has a lot of good info. There is a forum specifically for VOA's (virgin oil analysis) that will give you inside information on what exactly is in some more popular oils. There is even a guy in the UOA (used oil analysis) forum that has tested his oil after running it through his YZ250F. Kinda interesting...
Just one question (so far), where can a person obtain "break-in fluid"?
Good read, good info. Thanks again. 
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