Many
cars now come with a system that displays a message on the instrument
cluster indicating when it’s time for a change. Rants on the
Internet, however, would have you believe that such indicators are
the work of the devil—devilish automakers, that is, who program the
oil-life monitors to extend change intervals so that engines wear out
sooner, forcing motorists to buy new cars. But you can dismiss such
conspiracy thinking. Oil-life monitors do their job quite well. Oil
is an engine’s lifeblood, and like a blood test, an engine-oil
analysis can identify potential problems before they become
serious—and expensive.
Most
oil-monitoring systems don’t actually measure various substances in
the oil. Instead, they track driving habits, using algorithms that
take into account such variables as mileage, engine speeds, and
operating temperature to estimate when the oil is likely to be cruddy
enough to require a change.
The
monitors typically alert the driver to change the oil between 5,000
and 10,000 miles. But the interval could be shorter or longer
depending upon your driving routine. If most of your driving is
long-distance at relatively high speeds, the monitor may not indicate
a change for 12,000 or even 15,000 miles. If tootling for a few
minutes down the road to the market or mall is the only driving you
usually do, the monitor may go off in as little as 2,500 or 3,000
miles.
Oil
lubricates the engine’s internal moving parts, and short-distance
driving is particularly hard on motor oil. Moisture from condensation
and combustion gases form acids and sludge in the oil that inhibit
lubrication and accelerate wear. Allowing the oil to reach its
optimum operating temperature burns off contaminants—and that may
take up 20 or 30 minutes of driving, especially in colder weather.
Though
oil-life monitoring systems work well, you’ll still need to crack
open the good book—your car’s owner’s manual. And that means
reading the fine print. For instance, the manual may say not to
exceed 10,000 miles between changes despite the oil-life monitor’s
instructions. Or, it may specify an oil change once a year, even
though the car’s oil-life monitor hasn’t called for one. An
annual oil change also gives your mechanic a chance to inspect your
car and alert you to problems that might have developed during the
year.