If you’ve ever had trouble starting your car, your first instinct was probably to pop open the trunk and grab your jumper cables. But not all starting problems are caused by a faulty battery. In fact, worn out or defective spark plugs are often the culprit. And while most drivers have some basic knowledge of car batteries, spark plugs are usually a little more mysterious.
So how long do spark plugs last? And how do you know how often to change spark plugs? Let’s cover some fast facts about this critical component in your vehicle.
FACT #1: YOUR VEHICLE WOULDN’T START WITHOUT SPARK PLUGS
What do spark plugs do? Maybe the most important task of all: they help the engine start. Spark plugs are responsible for igniting the air/fuel mixture within the engine’s combustion chamber. So even if you have a well-oiled engine and a full tank of gas, you can’t use either of them without good spark plugs.
FACT #2: WHEN YOUR SPARK PLUGS ARE WORN OUT, YOU’LL PROBABLY NOTICE IT
In modern vehicles, the dashboard is your best friend—with a series of warning lights that will let you know instantly when a problem occurs. That goes for spark plug issues, too. When a spark plug, spark plug wire or coil pack begins to fail, the Malfunction Indicator Light (MIL), also called the Check Engine Light, may illuminate. In some cases, the light will even start flashing. This means that potentially catastrophic misfires are taking place, and you need to bring the vehicle in for service immediately.
FACT #3: DEFECTIVE SPARK PLUGS CAN CAUSE PROBLEMS EVERY TIME YOU DRIVE
Wondering how to tell if a spark plug is misfiring? Even before the MIL comes on, you may start to notice the signs of failing spark plugs. Defective spark plug symptoms can include problems with idling, acceleration, and fuel economy. Let’s look at a few in detail:
- Starting issues. Since spark plugs provide the literal spark that starts your engine, starting problems are one of the first signs of bad spark plugs. Worn out spark plugs have a harder time creating the spark that begins the internal combustion in your engine. If your engine stalls when trying to start, there could be a problem with your spark plugs or spark plug wires.
- Engine idling issues. If you have a newer car, there may be times when your engine is so quiet you can’t even hear it running. Modern engines are designed to run smoothly and quietly, so if you’re experiencing engine noise like rattling, pinging, or knocking, faulty spark plugs could be to blame.
- Fuel economy issues. When spark plugs are near the end of their life, your engine can no longer burn fuel efficiently. According to Automotive Service Excellence (ASE), a misfiring spark plug can reduce fuel efficiency by as much as 30%. So, if you’re finding yourself at the gas pump more often than you’d expect, it may indicate a problem with your spark plugs.
- Acceleration issues. No one knows your vehicle better than you. If you’ve noticed that your vehicle isn’t as responsive as normal, or that something feels different when you’re trying to accelerate, it could be caused by worn spark plugs.
FACT #4: YOU SHOULD CHANGE SPARK PLUGS EVERY 100K MILES OR SO
So, if good spark plugs are the key to avoiding these issues, how long do spark plugs last, exactly? The general rule of thumb about how often to change spark plugs is that they should be replaced after about 100,000 miles of driving. Your vehicle manufacturer likely recommends a specific interval, so review the suggested maintenance schedule in your owner’s manual to see how often to change spark plugs in your make and model. Or consult the trained technicians at your local Jiffy Lube®, who can evaluate your vehicle and suggest a schedule based on manufacturer recommendations.
Hopefully, spark plugs now feel a little less mysterious. And now that you know how often to change spark plugs, you can look forward to a smooth start every time you get in your vehicle.
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