[net.cycle] synthetic oil

rusty@sdcarl.UUCP (rusty c. wright) (08/13/83)

i was at the store buying oil for my motorcycle the other day,
i've always been using castrol because it claims to be better
for smaller, higher revving engines (my bike red lines at 10k).
while there i noticed something that i'd forgotten about;
synthetic oil. wanting to do only the best for my motorcycle i
was wondering if it might be better than the castrol. does
anybody know what the relative merits are of synthetic oil?
what are the disadvantages of it (besides a possibly higher
price)? are some brands of synthetic oil better than others?

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wookie@alice.UUCP (08/15/83)

Early synthetics had some problems but they seem to have improved these
oils so they do very well.  The problems you may run into are:

		1.  Synthetics have excellent film strength and so 
		    are typically fairly thin like 10 weight.  This 
		    improves gas mileage by reducing friction but
		    if the engine is worn or loosly fitted the oil 
		    pump may not be able to provide adequate flow
to maintain good pressure to all parts.

		2.  Because the oil is thinner it flows much faster
		    through the various parts.  It is thus unable
to pickup heat and carry it out of the engine.
		    This has been the problem in using synthetics
		    in racing.  The bearings overheat through lack
		    of cooling normally provided by the oil. (I think
		    the BTU capacity of the synthetics is also lower
                    than regular oil)

Otherwise the synthetics are great stuff and have been used in aircraft
turbines etc for years since regular oil can't do the job there.  If you
are not racing and the engine is tight they should work nicely and keep
your engine in better shape as they have better film strength and can
suspend combustion byproducts better than regular oils.

					Keith Bauer
					White Tiger Racing

rusty@sdcarl.UUCP (rusty c. wright) (08/26/83)

thanks to all for their replies to my query about synthetic oils.

the basic conclusion that i have come to from a talk to the person
in charge of the service department where i take my bike (which was
corroborated (sp?) by one or more replies) is that it is not a good
idea to switch over to a synthetic oil after having used a regular
oil previously for any period of time (including the break in period).
the reasoning is that regular oil creates a thicker film around things
and when you switch to the synthetic it creates a thinner film and so
things tend ``rattle around'' a bit more, also oil consumption can go
up because of this. the shop manager said that it is best to stick to
whatever oil the bike was broken in with; remember this if you want to
use some oil fancier than the dealer puts in the bike when they sell
it to you.

so, presumably if one started using a synthetic as soon as they bought
the bike (brand new) they might be able to. although one or more
person mentioned that because synthetic oils are more slippery that
they can cause problems with transmissions/clutches in motorcycles.

anyhow, i'll stick with good 'ol castrol.