Just some general comments on oil changes which reflect
my opinions based on some observations over the years:
The common perception of the importance of changing the
oil every 2,000 to 3,000 miles is a hold over from the days
before cars had positive crankcase ventilation and back
when the gasoline contained lead additives. A running
engine tends to pollute the lubricating oil with unburned
gasoline and water vapor and other compustion by products.
Getting the oil hot will boil off the unburned gas and water
vapor and the PCV system will purge the fumes out in a
more effective manner than will the draft system employed
earlier. The domestic manufacturers changed their oil
change recommendations from 3,000 to 6,000 mile
intervals with the introduction of PCV systems.
The elimination of tetra-ethyl lead from gasoline also
helps to keep the oil clean. Domestic manufacturers changed
their recommendations from 6,000 to 7,500 mile intervals with
the US change over to unleaded fuel.
As a concequence it is only necessary to change oil frequently
if the engine is crequently operated in a situation that doesn't
allow the oil to get good and warm frequently (ie: lots of short
trips).
Except for the daily drivers (who's cars fall under the regular
service regimine) our cars tend to sit idle for days (or weeks or
months) at a time. This idle time does not contribute the the
dilution or break down of the oil since gasoline wash down
and blow by only occure when the car is running (or immediately
after shut down). For these reasons it is better to let a car sit
idle over the winter than it is to "start it up and let it run for 10
minutes every week/month."
Also, keep in mind that, as a group, we are more likely to tear
apart an engine and rebuild it long before it is truely worn out
because we want to improve the esthetics of it or to increase
the power, or... or... or whatever! Because we want to rebuild it!
So a little accelerated wear is of little or no significance.
Soap box mode off
Dave Massey
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