A Guide to Automotive Gauges

Beyond the speedometer and fuel gauge, here's what to keep an eye on.

Connor Hoffman | 

Apr 12, 2024 | 3 min read

Manuel Carrillo III | Capital One

In everyday driving, the only gauges you might regularly glance at are the speedometer and the fuel gauge. If you've ever been curious about what the little genie's lamp is for or how you can use a trip odometer, read on.

Ford

Oil-Pressure Gauge

High-performance sports cars such as the Ford Mustang Shelby GT500 and Porsche 911 often have oil-pressure gauges that read the engine oil pressure in either psi or bars, a metric unit that equals roughly 14.5 psi. Your everyday commuter might only have an oil-pressure warning light that comes on when it detects a low oil level, which can severely damage the engine. Normal oil operating pressures vary by engine, but commonly range from 25 to 65 psi.

An oil-pressure light is different from the oil-maintenance light, which simply tells you when it's time to get an oil and filter change.

Nissan

Coolant-Temperature Gauge

Coolant is a glycol and water mixture that keeps your engine from dangerously overheating. The glycol, or antifreeze, keeps the fluid itself from freezing. Most modern cars use warning lights to tell you if your car has overheated, often with the symbol of a thermometer floating in a wave of coolant.

If your car has a temperature gauge, it's likely an indicator that points between H and C — hot and cold — or units of temperature. If you notice the coolant-temperature gauge start to creep up, pull over immediately and turn off the engine. Failing to do so could damage your engine.

Kara Snow | Capital One

Battery Voltage

Nearly all gas-powered cars use lead-acid batteries to start and run accessories in the car. As with the coolant-temperature gauge, most modern cars have switched to a simple warning light if something goes wrong, usually a symbol of a battery.

Some vehicles have gauges with numerals to show battery voltage. If the light illuminates, it may be time to replace your battery. It could be damaged or just worn out.

Nissan

Trip Odometer

While the odometer records every mile your car travels, the trip odometer, typically located at the bottom of the gauge cluster, records the distance traveled from the moment you set it.

It's helpful to track fuel economy or simply to see how far you've traveled on a cross-country road trip. Some drivers keep track of trip mileage for business reasons.

Dodge

Tachometer

The tachometer, which is typically a big round dial on the left of the gauge cluster, tells you how fast the engine is turning. Each numeral interval is in revolutions per minute (rpm), by the thousand.

Some of the highest-revving sports cars' engines can reach close to 10,000 rpm, but most daily driving resides around 1,500 to 2,500 rpm. In a car with a manual transmission, the tachometer can help you seamlessly shift into the next gear if you can match the engine revolutions properly.

Nissan

Boost Gauge

Some engines use forced induction, whether it be turbocharging or supercharging, to increase the amount of air density going into the cylinders. A boost gauge measures the pressure of the compressed air, or boost, being added to the engine.

The gauge can be standard equipped, or professionally installed on high-performance or even economy cars, from Porsche to Nissan. These gauges are helpful for making sure your car isn't getting more boost than the engine can handle, which could severely damage it.

Connor Hoffman

Connor Hoffman is a writer and editor based in Kansas City. Prior to becoming a freelance writer, he was an editor at a national car magazine and worked in communications at a major automaker. He loves off-roading and camping in his 4Runner, golfing (poorly), and shredding on his mountain bike.