Spark plugs are one of the most important—and most forgotten—parts of your engine’s tune-up. They don’t need changing as often as your oil, so it’s easy to forget about them until they start causing problems completely. To avoid a rough-running engine and poor gas mileage, let’s talk about how often to change spark plugs so we can give them timely attention.
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Why Do Spark Plugs Wear?
Before knowing when to change spark plugs, you should also learn the reasons for their deterioration.
Like most other engine parts, the plugs wear out over time. This process causes wear in two main ways:
Electrode erosion (The main reason)
Every single time a spark jumps the gap between the two metal points (the electrodes) on the plug, it vaporizes a microscopic amount of metal. It’s like a tiny sandblaster constantly eating away at the tip.
Over millions and millions of sparks, this erosion makes the gap wider. As the gap gets bigger, the ignition system has to work much harder to create a strong spark, which can lead to misfires, poor acceleration, and bad gas mileage.
Contamination (Fouling)
The inside of an engine isn’t perfectly clean. Over time, spark plugs can get coated with gunk from the combustion process, such as:
- Carbon: A black, sooty buildup from a rich fuel mixture or lots of short trips.
- Oil: A black, oily coating from an engine that is starting to wear internally.
This buildup acts like an insulator, smothering the spark and making it weak or preventing it from firing at all.
Problems Caused by Worn Out Spark Plugs
Used up spark plugs can create plenty of trouble. Besides affecting the engine performance, they also hit the gas mileage.
In response to how often to change spark plugs, vehicle manufacturers suggest waiting for 100,000 miles in case of extended-life plugs. However, plugs that have run for 80,000 miles are already four-fifths worn. Every function related to them starts suffering when the gap between plugs widens over time.
Worn out plugs can also seize the cylinder head and break it, costing an expensive repair job.
Even if your vehicle has extended-life spark plugs, checking them every 30,000 miles is a good practice. As you have to replace them sometimes down the road, it is better to change them sooner rather than later, before the car starts showing troubles.
Every time you examine the plugs, don’t forget to inspect the conditions of a few other items, including the brakes, tires, fuel filter, air filter, and charging system. Keeping these parts in good running condition and updated will help the vehicle perform at its peak power.
How Often To Change Spark Plugs?
The owner’s manual of your vehicle is the most authentic source to find out the changing routine of spark plugs. Most automakers recommend replacing it every 30,000 miles. This is the right duration if you are using stock products. But the actual timing may vary depending on a few other factors:
Check engine light
The light indicates plenty of engine problems and worn out spark plugs are one of them. The check engine light will be on or start flashing when either the electrode or the wire connecting them become worn. When that happens, you should check if your engine is misfiring.
Misfiring plugs put extra stress on the catalytic converter, increase exhaust emissions, and supply uneven power at the time of acceleration.
High-performance plugs
Some high-performance plugs combust more fuel by providing more sparks to the firing tip. As a result, the car can produce a bit more horsepower.
However, the electrode of these high-performance plugs wears thin faster. So, you will need to replace these plugs before the usual 30,000 miles.
Extended-life plugs
How often to change spark plugs when they are rated for an extended lifespan? In that case, you can definitely keep them longer than 30,000 miles. Plugs made of platinum and iridium are the most durable and the copper ones have the shortest life.
Acceleration and speedy driving
Do you like to rev your car and listen to the screeching of tires? Doing so makes the plugs to undergo additional wear and tear. Speeding up the car will require replacing the spark plugs more often.
Oil leaks
The base of a plug should be clean when you pull it out of the engine. If there is a trace of oil, you should look for a blown seal and change the plugs as soon as possible.
The engine will show some symptoms when it’s time to change the plugs. Examine the condition of the plugs and change them (if necessary) when the engine skips, stalls, or runs rough.
What To Keep In Mind When Changing The Spark Plugs?
Besides learning how often to change spark plugs, you should also keep a few things in mind to extend their lifespan.
Always use the same plug type when you are replacing the old ones. For example, if the default plugs are double platinum the new ones should also be double platinum style.
Also, don’t forget to check the spark plug wires because frayed wires can be another reason for engine misfiring. Change the wires if they are old and crispy before they cause a bigger problem.
