[I]Primarily RPM meters (also known as {aka} Tacho meter) are of concern to mechanics - for driver RPM meter help to note abrupt engine speed when not driving, and to manage gear shift to get better milage per gallon.. ( kilometers per litre )
equipment which is not standard on a vehicle can be added from after market accessories, in meters the VDO of Germany is best.
Further -
The RPM meter, or Tachometer, on your dashboard is used to show the driver how many revolutions per minute your engine is rotating at. This is to show the driver when they are approaching the mechanical limits, redline, of the engine.
If a driver in a manual transmission car does not shift before hitting the Redline of the engine they could damage their engine. Automatic transmissions typically protect the car by shifting before the redline automatically. Also in modern computer controlled ( EFI +ECU ) cars there is a fuel cutoff at Redline where the computer will stop feeding fuel to the engine before it would be damaged so the driver cannot accidentally exceed the redline.
Now that being said there is still a way to damage the engine if a driver of a manual transmission car is not watching their tachometer. If a driver were driving close to redline and downshifted to a lower gear the engine RPMS would increase very quickly and exceed the redline of the car and the fuel cutoff would not be able to stop this. The engine could be damaged by the driver this way.[/I]