Every driver relies on the information relayed by the auto gauges integrated into their vehicle's instrument cluster. They can relay a substantial amount of information, and give a helpful understanding of operating conditions. If you are unclear about what each gauge represents, keep reading below for more information:
Speedometer: This is one gauge you'll find in any car driven on the street and measures the speed of the car in either Miles per Hour (MPH) or Kilometers per Hour. Generally all new cars feature electronic speedometers, which are controlled using information gathered from various sensors. Speedometers are reasonably accurate from the factory, but large changes in tire size will require a recalibration.
Tachometer: This is a gauge that measures engine (Revolutions Per Minute) RPM. You won't find one on all cars, but they are especially useful when included with a manual transmission. A driver with a tuned ear won't need to look at the tachometer to know when to shift, but they can be very handy for checking for proper engine idle speed.
Engine Coolant Temperature: The coolant temperature gauge helps alert drivers if their engine is overheating. On older vehicles these gauges were fairly accurate and could give adequate warning in the event of an overheating situation. Modern gauges will generally indicate an "OK" reading for a wide range of temperatures. This means by the time the needle has finally moved out the range indicated as acceptable on the gauge, the engine may have already overheated. The best way to get an accurate coolant temperature reading on a modern car is with either an infrared thermometer, or by using a technician's scan tool to interact directly with temperature sensors. That being said, as long as the cooling system is maintained properly, overheating should never be an issue.
Oil Pressure: Unfortunately, these now fall into the same category as coolant temperature gauges. Oil pressure gauges should not be used for any type of accurate pressure reading. Many will simply act as an on/off switch, (indicating either full pressure or no pressure) without ever giving any type of accurate reading. In order to get a true oil pressure reading, an oil pressure gauge must be attached to the engines oil system.
Battery Voltage: Battery voltage gauges let you know how much battery life you have left. A multimeter is a device used to measure electrical voltage, and is an essential tool for inspecting electrical systems. Much like coolant temperature, battery voltage should generally be acceptable as long as the charging system (alternator and its associated wiring) are in good working order.
There are many companies offering gauges with the ability to measure anything automotive. When installed correctly, these gauges may be more accurate than factory components. Gauges are an excellent tool to monitor vehicle performance, but seldom give a complete picture without other important information. This is why it is important to have a trustworthy mechanic with the ability to diagnose and repair modern cars.