Some drivers take good care of their cars, while others treat their cars like family. No matter how attached you are to your car, it is important to keep your tachometer working properly. Your car tachometer measures your vehicle's RPMs and serves as a clear indicator of engine-related problems. A handheld tachometer acts the same way with a visible red light beam from a powerful LED, although the detection distance tends to vary across models. Although it is sometimes possible to repair a tachometer, in some instances, the unit requires replacement. If you want to maximize your fuel economy, choose a cruising RPM near the torque power for your daily commute. If you feel the need for speed, opt for an RPM near the horsepower peak for optimal driving performance. eBay offers a wide selection of tachometers sold by reputable sellers. Both new and used items are available in most cases.