Clinton News-Record, 1978-11-02, Page 38•
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Plugs Need Change
Every 10,000 Miles
A spark plug may ,look
good to the casual observer
after 15,000, 20,000 or even
30,000 miles.
° So why change plugs
after 10,000 miles of use
in your family car?,
There's a good reason
according to experts, The
.10,000mile. change -recom-
mendation is not* actually
based on the fad that
spark plugs are "worn out"
in the strictest sense after
10,000 miles of service.
This figure -- selected
after extensive spark plug
life tests - merely repre-
sents a safety factor be-
yond which plugs may
misfire under the sudden
demands of peak acceler-
ation or extremely heavy
load.
Gas Economy Drops
It also represents the
pair at which g en-
as ins to *aid.-., ll
•� , the carr lOatder
to start, power isbisti
passing.
A spark plug is. eon-
sidered warn out when it
reaches the point where it
is likely to misfire -- re-
gardless of its appearance.
And, contrary to popular
opinion, misfiring doesn't
necessarily mean the plug
didn't create a spark. It
means simply that _the
plug failed to ignite the
gasoline properly—wheth-
er a spark was produced
or not!
A new spark plug with
the correct gap setting
needs about 5,000 volts to
fire. However, as the plug
remains in service, con-
stant -heat and chemical
attack plus electrical ero-
sion cause the gap to be -
M
come wider, thus increas-
ing the amount of voltage
to fire the plug.
Gap Gets Wider
Spark plug gap growth
occurs at a rate of about
.001 inch for each 1,000
miles-of...:driving....Conse.-.
quently, a set of plugs that
has been in service for
10,000 miles generally will
have gaps that are about
.010 inch wider than the
originalettings and
higher voltage is needed
to make them spark.
And, this is only for
normal driving. Operating
the engine at very high
speed can decrease the
amount of coil voltage
available to fire the spark
plugs by 30 to 40 percent!
Accelerating to pass on a
- highway—may : practically
double the voltage burden
on the spark ping.
Needs bore Voltage
That's why misfiring is
first noticed while accel-
erating because it's here
that the plugs actually
can require more voltage
to produce 'a spark than
the ignition system is ca-
pable .of producing — es-
pecially if the plugs are
.badly worn.
Remember, as plugs re-
main in service, more volt-
age is needed to make
them spark. As the ignition
system ages, its ability
to produce high voltage
lessens. If the point is
reached where the spark
plugs require more voltage
to spark than-- the system
can produce, the spark
plugs misfire.
The Champion Spark Plug Company Economy Rally, conducted in San Diego and the
San Francisco area, began and ended at the gasoline punters where cars were filled
before, .and ,after the inn. Gasoline was carefully, measured to make sure accurateread-
ings of consumption were gathered to determine winners fairly.
Changing spark plugs at
10,000 mile intervals pre-
vents this from happening.
HANDLING SKIDS
If your car goes into a
skid on a wet or icy street,
turn the steering wheel in
the direction of the skid. Do
not jam on the brakes but
pump them gently,
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BRYON
PAF( f'. nn., .
Complete
ACHINE SHOP
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•