How often should oil and filter be changed?
Change oil and filter often enough to protect the engine from
premature wear and viscosity breakdown. For most cars and light
trucks, the standard recommendation is to change oil and filter
every six months or 3,000 miles, whichever comes first.
Most late model owner's manuals say that except for "Severe Service"
applications, oil change interval can be safely stretched to once a
year or every 7,500 miles, with filter changes at every other oil
change.
When auto makers make such recommendations, one assumes they are
based on extensive durability testing. After all, auto makers
themselves would have to bear the warranty costs should their
maintenance recommendations prove inadequate.
Except for Chrysler's 7/70 powertrain warranty, and a few others
that go up to 5/50 or 6/60, most new car powertrain warranties don't
go beyond 3/36. So where's the risk? There isn't any.
With proper maintenance, there is no reason an engine shouldn't go
100,000 miles or more without developing a thirst for oil. That is
why most oil companies, as well as aftermarket service
professionals, recommend changing oil and filter every six months or
3,000 miles.
They also make such recommendations because many motorists are not
aware that they should follow the "Severe Service" maintenance
schedule in their owner's manual, calling for oil and filter change
intervals of three to six months or 3,000 miles. Severe service (as
defined by auto makers themselves) includes:
- Making frequent short trips (less than five miles)
- Making frequent short trips (less than 10 miles) when temperatures
are below freezing
- Driving in hot weather stop-and-go traffic
- Extensive idling and/or low speed driving for long periods of time
(taxi, police, door-to-door delivery, etc.)
- Driving at sustained high speeds during hot weather
- Towing a trailer
- Driving in areas with heavy dust (gravel roads, construction
zones, etc.)
- Protective additives in a motor oil do not hold up as well under
such driving conditions for several reasons. If the engine is not
running long enough to get the oil hot, condensation and fuel vapors
will not boil off. Contaminants will accumulate in the crankcase,
leading to formation of corrosive acids and sludge.
Excessive idling and high operating temperatures from towing and
high speed driving during hot weather accelerate viscosity
breakdown. Exposure to dust can put dirt particles in the crankcase.
The filter also needs to be changed every time for two reasons.
Today's pint-sized filters do not contain as much filter material as
their quart-sized counterparts. The filter contains dirty oil that
can contaminate fresh oil added during an oil change.
Considering what four quarts of oil and a filter cost, versus the
cost of replacing an engine, it is better to change oil and filter a
little more often than might be absolutely necessary rather than
risk not changing it often enough.
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