A tune up checks such things as your cars ignition timing (when the spark ignites the fuel in your engine) and the fuel mixtures. An ideal fuel mixture should be 15 parts air mixed with 1 part fuel. This means that you will have good power and fuel economy. If something within your engine causes these mixtures to vary, you will experience poor fuel economy and a rough running engine. Again in extreme cases this can cause complete (and expensive) engine failure.
Luckily most modern cars have moved away from carburettors to far more accurate fuel injection systems run by onboard computers. However, your engines fuel and ignition systems still require maintenance such as spark plugs, ignition leads, fuel filters and injector maintenance. Make sure you ask about a tune up next time you visit Berry Motor Group.