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Our police vehicles rarely sat long enough for the engine to cool which I
thought would really shorten their life span and be extremely tough on the
oil. These vehicles were passed from shift to shift, 24 hours a day, seven
days a week, all city driving and under all kinds of extreme demands that you
would never do to your vehicle. We found no oil break down between 2500 mile
oil changes! When engines had to be torn down, which didn't happen often,
they had no unusual friction wear... in fact they generally looked better
than expected.
My theory is the engine was kept at an ideal temperature and this was easier
on it than had there been lots of cold starts and repeated warm ups and
cooling off periods. The oil was also kept at a constant viscosity and the
metal temperature did not fluctuate much, thereby keeping clearance
tolerances as uniform as possible. There was little chance of any moisture
build up or other contaminates forming from repeated hot to cold, cold to
hot, cycling as you would in your vehicle.
After about two years or a bit less the cars were sold off to the public and
the engines were generally darn good, even after 120,000 miles of city
driving!
The lesson I learned was running an engine constantly does not affect it as
much as short trips and infrequent use. Those short trips seem to greatly
shorten the life of oil and may lead to premature engine failure if not
flushed regularly. Frequent oil change is cheap insurance, I reckon.
We used Penz, Quaker State and Havoline, the cleanest engines seemed to be
from Quaker State, but couldn't tell you why. Mechanics liked Castrol well
enough, but we couldn't buy it in bulk for some reason... so it didn't get
used.
By the way... we tried some of those oil additives that claim you can run an
engine without oil if you use their product or reduce friction by 50%,
increase mileage, etc.... found them to be absolutely worthless.
Jack Lee
(Sunny California)
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