Spark plugs are a vital part of your vehicle’s engine. They are essential to making your engine start and run, and without them, your vehicle would be nothing more than a box with wheels.
Despite this, they are often overlooked in a routine car maintenance schedule. Just like every other engine component, they wear out with use and time, and heavy usage makes them wear out more quickly.
Thankfully, replacing spark plugs (just like changing your vehicle’s oil), is not that complicated of a process.
Buying new plugs is not expensive at all, a few simple tools can get the job done, and spark plug change intervals have become longer thanks to better materials and technology.
Let’s take a look at how long you can (and should) drive your vehicle before it’s time to change your spark plugs.
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What Are Spark Plugs?
These are small devices inserted into the combustion chamber of an engine which create a spark that makes an engine start and run.
They have two electrodes with a gap between them, over which electricity travels and creates a spark.
The spark ignites the air-fuel mixture entering the engine through the air intake and fuel injectors, pushing the engine’s pistons down and creating the engine’s power.
If this spark doesn’t occur or is prevented from firing at its optimal capacity, the engine will struggle to start, run correctly, or even stall.
Why Should You Change the Spark Plugs in Your Vehicle?
Any component inside the engine is subjected to large amounts of frictional heat from moving parts, pressurized fuel within the fuel system, and pressure from the explosions which occur inside the combustion chamber.
Because spark plugs are inserted into the combustion chamber, they are subjected to each of these forces. They all contribute to several reasons you should change your spark plugs.
A literal spark jumps from the ground electrode to the center electrode on the tip of the spark plug.
As this occurs over thousands of times per minute over the life of the electrode, the electrodes wear and the spark becomes less efficient.
As fuel combusts within the combustion chamber, the remnants of these explosions can produce a thick carbon buildup on the tip of the spark plug if more fuel than oxygen enters the engine.
This buildup can prevent the spark from firing correctly, and will cause a less efficient or non-existent spark.
This fouling is especially common in vehicles with gasoline direct injection fuel systems, with an overly rich injection of fuel into the engine, or when poor quality gasoline is consistently used for fueling your vehicle.
Heat and Pressure
Many people take for granted that there is a literal explosion occurring within their engines thousands of times per minute.
These explosions cause massive amounts of heat and pressure repeatedly within the combustion chamber.
The tip of each spark plug is exposed to each explosion, which inevitably causes wear over time.
Seals and gaskets are often one of the first things to wear out in a vehicle, as they are often made of rubber, plastic, or silicone.
If you have a worn O-ring seal, oil can leak onto the tip of the plug, preventing a spark.
This becomes a more likely issue the older your vehicle becomes.
How Often Should You Replace Spark Plugs?
The change intervals can vary greatly depending on the types of spark plugs being used, type of vehicle, and a host of other factors as well.
With that being said, there are four main milestone change intervals for just about every vehicle today.
Every 20,000 to 30,000 Miles
30,000 miles has been accepted for years as the most common replacement interval.
Even today, low quality spark plugs or those made with a less durable material (such as copper) should be replaced every 20,000 to 30,000 miles.
This shorter lifespan is becoming more uncommon as materials and technology have improved (and continue to improve) over the years, allowing better quality spark plugs with a greater resistance to wear to be manufactured.
Every 60,000 Miles
60,000 miles is a much more common change interval nowadays.
Most quality spark plugs are suggested to be changed at 60,000 miles, and this is currently the most widely accepted change interval for most spark plug types of today.
Every 80,000-100,000 Miles
80,000 to 100,000 miles is slowly becoming the new standard for high quality spark plug replacement intervals.
Many mechanics and manufacturers are beginning to set 80,000 miles as the new standard for the industry, but most mechanics still suggest changing them sooner.
Most manufacturers advise that you can travel at least 80,000 miles before a change is required for the newest vehicles.
Every 100,000 Miles or More
100,000 mile change intervals is pushing the envelope, but it is becoming possible in the best high-performance spark plugs on the market.
Most spark plugs, including high-performance ones, are still going to be worn by the time 100,000 miles come around.
However, depending on driving conditions, they may not be worn to the point where performance is dramatically affected.
Watch the following video to find out more information about when to change your spark plugs.
What Factors Affect How Often You Should Replace the Spark Plugs?
There are many factors that affect whether you should change your spark plugs sooner than recommended, or whether you will be safe to wait some extra time.
What Type of Spark Plug Are You Using?
Spark plugs are made of different types of materials.
Copper, iridium, and platinum are common metals used in manufacturing them, and all have different lifespans.
Copper is good for electrical current, but doesn’t last as long as both iridium and platinum. Iridium and platinum are more durable materials, but the electrical current doesn’t flow as freely through either metal.
How Do You Drive Your Vehicle?
Vehicles that are driven hard usually require more frequent spark plug changes.
Stop-and-go traffic, frequent towing, and spirited driving all contribute to a high wear rate.
Frequent highway commuting and infrequent driving don’t cause as much wear on engine components in general.
Is There Any Oil Leaking onto Your Spark Plugs?
If you know your vehicle is leaking oil onto the spark plugs, you will need to change them more often.
As oil leaks onto the spark plugs, they will corrode faster, and there will be a greater change that carbon buildup will result from unburned fuel.
O-ring seal replacements will usually fix this issue, but not always.
How Old Is Your Vehicle?
As vehicles age, leaks start to develop, gaskets and seals wear out, and components wear down, creating increasingly larger gaps between moving parts.
Due to this added wear, they need to be examined more often for premature wear, and the spark plugs possibly should be changed more frequently.
What Are Some Warning Signs That Your Spark Plugs Are Overdue to Be Changed?
If you suspect or know that you’ve likely waited too long to replace your spark plugs, or you just don’t know the last time they were changed, there are some warning signs that may alert you that you have a bad spark plug and an immediate change is needed.
If you don’t/haven’t experienced any of these symptoms with your car as of late, then you probably have good spark plugs.
Your Engine Is Idling Roughly
When spark plugs become fouled or there is oil leaking onto the tips of the plugs, the spark is prohibited from firing correctly or at all.
This can cause the engine to hesitate, which will make it run at a rough idle.
Your Engine Stalls
If the spark plugs become completely fouled, no spark will be produced, no combustion will occur, and your engine could stall.
You Can’t Start Your Engine
Just like the lack of spark in the spark plugs can cause an engine to stall, it can also prevent it from starting again.
This is especially common when there is oil leaking onto the tip of the plugs.
Oil doesn’t have a chance to burn off in the combustion chamber when the engine is on. Droplets of oil can prevent any spark from occurring at all.
Your Vehicle Experiences Slow or Jerky Acceleration
If your spark plugs haven’t been changed in a while, your vehicle could experience decreased performance due to the decreased ability to produce a spark.
A car that has trouble accelerating, or your car jerks when accelerating, is a prime example of that.
Your Check Engine Light Is On
When your check engine light comes on, it could mean a number of different issues, one of which could be a fault tripped by a spark plug issue.
(Remember that a flashing check engine light could signal serious trouble).
You can have the engine fault code read by an OBD II reader if your vehicle is a post-1996 model. This can very likely be the case if you drive a pre-owned vehicle. If the code signifies a spark plug-related issue, you can then be sure that it’s time to change them.
Your Gas Mileage Is Suffering
If your spark plugs are performing poorly, chances are that your gas mileage is also suffering.
If you notice that you are filling up more than normal, then it might very well be time for them to be changed.
Your Engine Has a Misfire
A misfire is one of the most serious issues your engine could encounter, and it could be caused by the lack of spark being produced by a spark plug.
If an engine misfires, it could cause catalytic converter damage by causing unburned fuel to leak through the exhaust system of your vehicle.
This problem could be caused by more than just worn out spark plugs, but examining them to see if they need to be changed is always a good place to start.
Are There Any Other Tips I Should Know About Spark Plug Change Intervals?
First things first, always be sure to consult your owner’s manual for accurate information about this. Your owner’s manual will let you know the exact timeframe in which you should change your spark plugs.
It is best to cross-check any new spark plug installation with the guide provided in your owner’s manual. It will tell the proper kind your vehicle requires, what tools you will need, and how to change the plugs yourself.
Also, keep in mind that you know your vehicle better than anybody else. So, you will always be the first to notice if your vehicle isn’t running correctly, and whenever something unusual is going on.
It is also important that you don’t ignore when this happens. If your spark plugs aren’t operating correctly, severe damage could occur within your engine, potentially causing thousands and thousands of dollars in damage.
Last but not least, just because a certain spark plug, mechanic, or even your owner’s manual says you should change the spark plugs at a certain mileage doesn’t mean you can’t change them any sooner if necessary.
If you know that you run your vehicle hard or that your vehicle isn’t performing as well as it usually does, change the spark plugs!
Wrapping it Up
Without spark plugs, your vehicle wouldn’t be able to start or run. Despite this, they are often not considered to be that important in preventative car maintenance, which is a huge mistake – to say the least.
Keeping them functioning correctly will not only keep your engine running correctly, but it will also prevent damage from occurring should your spark plugs fail due to excess wear.
Nowadays, most manufacturers and mechanics recommend that you stick to a changing schedule once every 30,000 to 60,000 miles, or else you’ll risk ending up with failing spark plugs.
With that being said, some manufacturers are pushing the spark plug change intervals to 80,000 to 100,000 miles along with some high-performance spark plugs.
However, that doesn’t mean that you won’t ever need to change them sooner to maintain the health of your engine. You know your vehicle, and you will know if/when it starts to run incorrectly!
Being informed and knowing when to change your spark plugs will be one of the best and easiest things you can do to keep your vehicle running like it should.