Most modern vehicles don't need to be "tuned"
in the conventional sense as was required of earlier
engines, however, the spark plugs and wires in today's
engines still wear out during the normal course of business.
Worn plugs and wires make the engine less efficient,
using more fuel than a
properly tuned engine.
Most engines need to be
tuned up every 30,000 to 90,000 miles.