Professional Mechanic
An auto mechanic (or car mechanic in British English and motor mechanic in Australian English) is a mechanic with a variety of automobile makes or either in a specific area or in a specific make of automobile. 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 dis-assembly 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.
http://en.wikipedia.org/wiki/Auto_mechanic
Auto Repair Service
Automotive garages and repair shops can be divided into several categories.
Firstly, there are the auto parts stores or motor factors who also maintain service operations. This is not common in the United Kingdom but more common in the US.
A majority of automobile repair workshops are independently owned and operated businesses. These may also include regional or national chains and franchises including OEM car dealership sites. In the US, these sites are commonly certified by their respective manufacturer to perform warranty and recall repairs by that manufacturer or distributor. Independent automobile repair shops in the US may also achieve certification through manufacturer sponsored programs. In the European Union a recent law (The EC Block Exemption Regulation 1400/2002 (October 2003[2])) allows motorists more flexibility in selecting where they can get their car serviced.
Thanks to this legislation maintenance and service work does not have to be done by the main dealer as long as the garage uses Original Equipment ‘Matching Quality’ parts, and are recorded as such, and the garage follow the manufacturer’s service schedules.
http://en.wikipedia.org/wiki/Automobile_repair_shop