Evening star., 1921-04-24

| One of the most common mistaken
ideas" about oils is the theory that
! heavier oils should be used in worn
| engines, says the Gargoyle.
| This mistaken idea has been called
oils. In other words. all that is nee
essary to determine what grade of oil
to use is to look at the speedometer
on your car, and after certain periods
of mileage. change to the next heavier
grade of oil.
For example. many car owners be-
lieve that a ]ight-bodied oil will cor
rectly lubricate their cars for the
| first 900 miles or SO. and that after
tha. they will need a medium Sodi ed
their car for fifteen or twenty thou
sand miles. they need a heavy-bodied
oil.
The average man, with no knowl-
edge of automobile construction and
design. argues that this change In
the body of the oil used is necessary
because the cylinder walls and pis-
ton rings become worm
Four Mistaken ideas.
It is found that it is based upon
four mistaken ideas, which are as
follows
Mistaken idea No /. That wear takes
place at substantially the same rate
in all makes and types of engines un-
der all conditions of service.
This idea entirely ignores the TACT
that there are wide variations in the
materials used for cylinders. pistons
and piston rings in different makes OF
cars. There are also differences In de-
sign, proportions and manufacturing
processes This theory also assumes
that all owners will accord their cars
the same care.
1t must be evident that variations
in any Of these factors will largely
affect the rate with which wear VIII
take place and consequently VIII
make the mileage basis for deter
mining the proper lubricant very in
accurate.
1t is we'll known that the rate OF
wear Of aluminium and cast iron pis-
tons varies widely and that the care
exercised in seasoning" and nnlsn-
ing cylinders and pistons materially
affects the life Of these parts: some
owners will take no care Wnate's
of their engines and may orlVe ~
high speeds. Others will give proper
attention to fabrication ana ol'e
their cars with care.
For these reasons it must be plainly
evident that any system attempting
to determine the proper lubricant loI
all cars on a fixed mileage oasls
alone must yield results which are
relied upon.
Another Wrong Impression.
Mistaken idea No. 2. That from
the time the engine is new wear is
uniformly progressive in proportion
to the mileage of the vehicle.
When engines are new che smootn-
ness of the metallic surfaces comlns
in contact with one another depenos
on the manufacturing methods em-
ployed in the finishing OF the sur
faces
The ideal condition would be the
lapping-in, or finishing. OF these sur
faces to give them q high polish.
completely eliminating al al ,SN ,oaE manns nnsss
facturer in production. t..
The methods usually employed IN
the quantity production OF automopiIe
engines do not permit OF hignly nm
ished surfaces being secured. Ike
ing such highly polished and anished q
surfaces would necessitate high costs
in production and eventually mean
higher cost to the purchaser OK the
car.
nerfs Of new cars Of many different
makes has conclusively proved that
the engines, when turned out oy the
manufacturer. are run-ln ohi5 -
limited degree: consequently. When
the car is received oy tne t;ii snne.
the metallic surfaces are BILL o"iie
Reoause Of this it is necessary for
the purchaser Of the car to operAte
his engine at moderate speeds sno
the rubbing surfaces wear to pro-
duce running fits. During this Pc
riod, however. it is not necessary 20
use a lighter oil than is correct 1of
the car when run-in.
As the parts wear IN: ,.arenc.s .ns.e 70
the running Ats required.
Once these polished bearing sur
faces and running clearances are pro-
duced as a result Of engine use. very
little wear will occur e1 fGr many .noe- sno.-
lubrication is provided: It must,
therefore. be true that II wear takes
Mace to any appreciable extent, such
wear is directly due to poor 1uofi-
eating value Of the oil used or, IN
rare instances. to poor design or ma
When wear has progressed to such
an extent that the piston rings pos
sess perceptible up and down move
ment, the pounding action OF the
rings on the sides of their grooves
tends to increase the enlargement at
a very rapid rate. This is the point at
which trouble from oil pumping usu-
ally commences. Under this condition
the clearances have become so large
that no oil. regardless Of body or
character. will prevent oil pumping
or overcome blow-by.
To summarize the progress Of wear
we have, hrst, the running-in per1od
during which wear Is slight out
ranid: next. the period in which the
.1 spse;., n0 on