The right set of gauges can be a valuable tool for keeping an eye on what is going on under the hood. Unfortunately, many cars leave the factory without an adequate set of gauges. Some cars have only a speedometer and a fuel gauge. A few cars have been known to use “binary gauges,” usually to indicate oil pressure. These “gauges” are actually controlled by an on/off switch, so the only readings are “acceptable” and “too low.”

The aftermarket sells gauges to monitor a wide variety of functions, and these gauges sometimes come with a baffling variety of options. Some are simply issues of how the gauge looks, since it is easy for gauge manufacturers to change the color and materials they use. Others affect the way the gauge installs or operates. ...

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