Question:
I've been told it's important to "break
in" a new car - is there a right way to
do it?
Answer:
It can be important to "break in a car" --- some more than others,
when components are manufactured /machined, if you
look under a microscope for example, you will see that even on a surface which is quite
shiny that microscopically there are bumps and inclusions on the surface.
When these surfaces rub against each other these bumps if you will wear off and the two
surfaces kind of conform to each other. In the case of rotating or
sliding parts this is especially true and there are lots of these inside the engine
and drivetrain.
In the engine for example, we have oil that is supposed to
help keep metal to metal contact from occurring these little bumps can even
protrude through the oil film and touch each other,
the so called break in is the planned wearing of the parts and components to each others shape and getting
rid of these small bumps etc. One good example is the piston rings they
don't actually seal properly until they wear a bit and conform to the cylinder
wall that they are sliding up and down against. How long the break in period is
then varies from manufacturer to manufacturer depending on the quality and
types of materials that they use in their product line.
Trust the written word of the manufacturer that is written in the
manual or operating hand book not some verbal gobble from the salesman when looking
for recommendations on break in a lot of these guys have never even read the
book they are just regurgitating stuff they think that they heard somewhere in
there "career" and there are some wild old wives tales about what's good for an
engine
When it comes to suspension most vehicles have a lot of rubber in the
moving areas of the suspension to isolate the passenger from all the nasty
road noises so break in really doesn't apply except on the odd specialty vehicle
that still might have real bearings etc. in the suspension. Now with all this
rubber the cars will settle so alignments etc. can change as the suspension gets
time of use on it but this is a different phenomena as it will continually change
right up until the time of vehicle death.
When we decide to race a car with rubber suspension it is said that the handling is better if the cars have a
few moles on them. There is truth to this as the suspension settles it gets
a bit more stable and changes at a slower rate.
So some competitors will actually drive the car on the street for a while to settle it in - - more
professional teams will actually disassemble the components and look at what
makes the car settle and scientifically figure out how to duplicate the
phenomena under more controllable conditions in order to get the best known
effects. For racing this is the right way !
In the case of a race engine the engines will be tested on a
dynamometer and special break in oil may be used that has special properties to wear
the engine in under strictly controlled conditions.
When the engine is ready for installation it is ready to perform at peak output.
Other driveline components such as gear boxes or differentials also
wear in the oil manufacturers in this case actually put stuff in the oil to allow
the break in to occur and still the proper lubrication to take place by having
some of the additive package attack the metal component surface and help the wear
process, this additive is used up quickly and what's left is a usable oil
for lubrication in regular service. If differential oil is change too
frequently it can actually be detrimental and cause some deterioration of
the metal gear surfaces with an over dose of the very strong additive
package. The manufacturers are basically relying on the oil very seldom being
changed in the differential .
In summary driving the vehicle at varied
rpm's and at less than peak performance, for the first few miles of operation, will help extend the life
of some vehicles and won't hurt the rest so its a good thing !
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