When to Replace Subaru Spark Plugs

Advanced Subaru technology means that spark plugs last much longer than they used to, but with Subarus lasting longer too, it’s important to know the signs that your spark plugs need to be replaced. While your owner’s manual will give you an idea of when to expect your spark plugs will need to be replaced, your driving habits and extreme climates might change the amount of time or miles you’ll get out of your spark plugs.

Our experts at South Shore Subaru, your Long Island Subaru dealership, have done the research for you to recognize the signs of failing spark plugs before you wake up to a car that won’t start.

What do Spark Plugs do?

Before diving into the signs that your spark plugs need to be replaced, it’s important to understand the purpose of spark plugs. In the engine, the spark plug is what ignites the mixture of air and fuel in the cylinders to get your car started. When your spark plugs fail, your car won’t start. However, the following problems are warning signs that your spark plugs may be on their way out.

Trouble Starting Your Subaru

If you frequently turn your key in the ignition and find that the car sputters, shakes, or takes longer than usual to start, your spark plugs might be to blame. Over time, debris begins to build up on spark plugs and wires corrode, making it more difficult for your spark plugs to get enough power to ignite the fuel and air mixture to start your car. This may even begin to drain your battery as the spark plugs will need more power as your spark plugs become less efficient.

If you find that this only happens in very cold weather, it may not mean you need to run to the mechanic. Lower temperatures make it harder for spark plugs to function properly. If you find your car is consistently hard-starting, your trusted mechanic should take a look at your car as soon as possible.

Rough Idling

Your engine should sound smooth and constant, particularly when idling. If you find yourself wondering why your vehicle is louder than normal at stop lights or feel your car shaking or vibrating when you stop, your spark plugs could be to blame.


Any time you hear rattling noises coming from your car, this should be a cause for concern. While there are many causes of rattling noises, one reason could be spark plug failure. When spark plugs begin to fail, it causes the cylinders in your engine to misfire, causing a rattling noise as the parts of the engine fire out of sync. No matter it’s your spark plug or something else, if you hear rattling noises at any time while driving or idling, you should take your car to a trusted mechanic immediately to prevent further damage.

Decreased Fuel Efficiency

This warning sign isn’t always intuitive. Contrary to popular belief, spark plugs fire throughout your entire drive. When spark plugs begin to corrode, your engine has to work harder to fire consistently. As discussed above, the cylinders in your vehicle begin to misfire and spark plugs draw more power from your engine to keep your car running. This means that your car begins to use energy less efficiently, causing your to have to stop at the gas station more often. If you find that a full tank isn’t taking you as far, there are many other issues that could be going on. If you start to notice less fuel efficiency along with other issues like a rough start or rattling, your spark plugs could be at the root of the issue.

How South Shore Subaru Can Help

Nothing is worse than running late for work in the morning, only to find that your car won’t start. You can use our scheduled maintenance lookup service so scheduled maintenance doesn’t creep up on you without notice. If you find that your Subaru is starting to show signs of spark plug failure, our factory-trained service center can help you find the source of the issue to get your car running like new again – you can even schedule your appointment online!

Our team at South Shore Subaru, your local Long Island Subaru dealership, is there to help no matter you’re buying a new car or hoping to keep yours running like new for years to come!

Categories: Service, Parts
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