In repairing cars, their main role is to diagnose the problem accurately
and quickly. They often have to quote prices for their customers
before commencing work or after partial disassembly for inspection.
Their job may involve the repair of a specific part or the replacement
of one or more parts as assemblies.
Basic vehicle maintenance is a fundamental part of a mechanic's
work in modern industrialized countries while in others they are
only consulted when a vehicle is already showing signs of malfunction.
Preventative maintenance is also a fundamental part of a mechanic's
job, but this is not possible in the case of vehicles that are not
regularly maintained by a mechanic.
One misunderstood aspect of preventative maintenance is scheduled
replacement of various parts, which occurs before failure to avoid
far more expensive damage. Because this means that parts are replaced
before any problem is observed, many vehicle owners will not understand
why the expense is necessary.