How Long Do Glow Plugs Last In A Diesel Engine?

Glow plugs are a diesel engine's best friend when the temperatures get low. In fact, they're essential to keep your engine working properly throughout the winter. As a rule, the number of glow plugs in a diesel engine matches the number of cylinders. So, if you have a six-cylinder machine, then you've got six glow plugs, which for a maintenance-minded owner means six extra components that require consistent care. How long can you expect the glow plugs in a diesel engine to last, though?

Underwhelming as it is, the mileage of these particular plugs will depend on a variety of factors, at least according to manufacturers themselves. Nittera, for instance, puts the estimate at approximately 100,000 miles, but notes that the condition of the engine, operating conditions, and the overall maintenance of the machinery will impact the overall lifespan of the glow plugs. Beru, another prominent glow plug manufacturer, didn't provide clear figures, but did add that climate conditions and the frequency directly correlate to how long glow plugs last. According to Beru, frequent cold starting is the most problematic for the components and can make the glow plugs age a lot faster than intended.

Though spark plugs are something mechanics recommend replacing quite often when you're driving a gasoline-powered car, glow plugs in diesel engines give you a bit more leeway. This isn't all that surprising, considering that glow plugs are technically there to ignite when the temperatures are low to help the fuel ignite and run a bit easier. As such, you can theoretically drive the car even if one of the glow plugs goes bad.

However, while it's okay to do so in a pinch, driving with multiple dead glow plugs will make the car run worse. Rough idling is common in such a scenario, and you'll definitely notice the engine vibrate harder than it's supposed to. Since glow plugs are there to aid the combustion process, you may also notice that when they're gone, the engine will struggle to produce enough power, meaning that you'll have to contend with using even more fuel.

When you put it all together, driving in such a state will cost you more money in the long term compared to replacing the entire set. A new set of glow plugs may run you between $300 and $900, including labor (depending on the number of cylinders), but considering the gas prices, it's a worthy investment since it will help you use less fuel in the winter. So, the moment you experience hard starting, misfiring, or rough idling (all of which are common occurrences when glow plugs go kaput), maybe it's time to get it checked out for the sake of conserving all that gas.