Spark plugs ignite the fuel mixture as it enters your engine’s cylinders – allowing the engine to run normally.
When they start to go out, you’ll have issues with everything from starting to normal running. And, you might have inconsistent firing or misfiring, especially as you accelerate or ask more from your engine.
The bad news is that even a single dead spark plug can throw off your entire engine and that can cause damage to the fuel injectors and cylinders if you keep driving.
The good news is that spark plugs are cheap and often easy to replace.
In fact, the average cost of replacing spark plugs is $50-$200. Here, you can expect to pay $5-$25 per spark plug. Cars need one per cylinder, or an average of 4 but no more than 8. In addition, you’ll pay $60-$250 for labor.
The table below shows a quick price comparison of spark plug replacement cost estimates from reputable suppliers:
|Supplier||Labor||Spark Plug Set Cost|
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How Much Does Spark Plug Replacement Cost?*
Spark plugs are low cost and relatively easy to install. In most cases, you can replace a full set in less than an hour.
So, often, mechanics will charge their minimum rate. However, the cost of replacing spark plugs in your vehicle depends on factors like engine accessibility, engine cylinders, and the condition of the engine.
For example, some require that you simply screw out the spark plugs and replace them. Others require taking the valve cover off first. So, costs vary by vehicle.
The following chart includes cost estimates for replacing your spark plugs in 10 popular models.
|Vehicle||Spark Plug Cost (per set)||Labor Cost|
|Lexus Rx 350||$102-$155||$178-$589|
*Note: Prices are estimates and were correct at the time of writing (February 2022). Cost estimates may have changed since, our figures should be used as a starting point for your own research.
Spark Plug Replacement Price Factors
The normal cost of spark plug replacement can range between $150 and $600+.
Here, factors normally include engine accessibility, make and model, and the cost of the parts.
Make and Model
The make and model of your vehicle is always the most influential factor in the cost of parts.
For example, if you have a Lexus, you can expect a pack of spark plugs to start at around $100. If you have a Honda, you can expect it to start at around $12-$17.
That’s in part because different manufacturers have different requirements for spark plugs. However, it’s also about brand. If you choose an aftermarket brand, you can normally cut costs, even for luxury cars.
In addition, the make and model affect other factors. For example, how familiar your mechanic is with the car. Or, if they have the parts on hand.
The more common your car is, the cheaper it is to service, because mechanics are more familiar with it.
Type of Spark Plug
Spark plugs are sold in four basic types. Here, the type of spark plug impacts efficacy and longevity. The main types are:
- Copper – Copper or nickel alloy spark plugs. These are necessary for most older vehicles, especially anything manufactured pre-1980. However, they’re not the best fit for most modern cars. You’ll get 15,000-30,000 miles out of most of them.
- Platinum – Platinum spark plugs are copper spark plugs with a platinum disc on the central electrode. This can more than double the durability of the spark plug. Here, you can expect anywhere from 3,0,000 to 100,000 miles on your spark plug. These are the standard for most systems. They normally cost $5-$15 per depending on the manufacturer.
- Double Platinum – Double platinum spark plugs fire twice during the compression stroke cylinder and the exhaust stroke’s cylinder. This means the secondary spark is wasted. However, the system is more reliable and it’s the only thing you can use in a waste spark system. On the other hand, you should not use it in an electronic distributor less ignition system.
- Iridium – Iridium are the longest lasting spark plugs. They last longer, require less voltage, and can start the car with less current. However, they’re also more expensive. You can expect to pay around $20 per spark plug for most brands. On the other hand, these spark plugs can last 100,000 miles or more, so they may be well worth the money.
This specifically refers to the type of metal used in the central and side electrodes of the spark plug. And, they’re listed in ascending order of cost.
You can often buy copper spark plugs for $2-$5 each, especially aftermarket. But, they won’t last as long, and they aren’t as efficient.
Aftermarket or OEM
If you buy an original equipment manufacturer spark plug, you will always pay more than if you buy aftermarket of the same quality.
However, moving to aftermarket parts also allows you to choose iridium or other performance parts that your dealer might not offer.
Therefore, aftermarket parts might not save you money. However, it can.
If you get low-end platinum spark plugs, you can expect to pay an average of $2-$7 each. Depending on how many cylinders your car has, that means you’ll pay just $8-$56 for a full set.
Cost of Labor
Labor costs are the largest part of replacing spark plugs. Here, you’ll have to remove the valve cover and the manifold in most cars.
In some rare cases, you might also have to remove other parts of the engine. However, that is unlikely. In addition, if you have an older car with a carburetor, they’ll be even easier to access.
Here, you can normally count on about an hour of labor to replace most spark plugs. If you have a specialty job or are getting other work done, it might go up to four.
In addition, some dealership and chain shops will charge a minimum number of hours. For example, some dealerships might charge an hour per spark plug – which is more than they need.
Some engines are also more complicated and might require more time to take apart.
4 Symptoms of Bad Spark Plugs
If your spark plugs are going out, you’ll likely notice when starting the engine. However, there are a few other symptoms you can keep an eye out for.
The following four symptoms are the most common.
1. Difficulty Starting
The first and most common sign of bad spark plugs is that your engine might have difficulty starting. You normally won’t notice this until your car has been sitting for at least a few hours.
So, you’ll want to pay attention in the morning or after getting off work. If your car is harder to start it might be that one or more of your spark plugs isn’t firing correctly.
Why is the ignition the first place you notice spark plug issues? Combustion engines require a stronger spark for ignition. So the spark plugs have to work at their best when you turn the ignition.
If one or more doesn’t perform well, it shows there first. You won’t notice during normal running until the spark plug gets worse or fails completely.
2. Knocking Engine
Bad spark plugs can cause your engine to make a knocking sound. This happens because the spark plug misses a round or doesn’t fully ignite all the fuel.
Then, the fuel vapor ignites outside of the cylinder, resulting in a knocking sound. This is the most common cause of engine knocking. Luckily, you can also fix it in about an hour.
Misfiring is caused by the exact same issue as knocking. Your spark plugs occasionally aren’t creating enough spark to ignite the cylinder.
Then, the engine gaps in one or more of the cylinders and you lose power. This can eat into your fuel usage. It also means your vehicle will be operating at significantly less than full power.
4. Rough Idling
The colder your engine is, the more power spark plugs need to channel to generate a spark to ignite the fuel.
If you’re idling the engine after startup and it’s skipping, missing, or misfiring, the spark plugs are likely the issue.
That’s especially true if you’re noticing that the engine just struggles to start and idle on cold mornings and if idling gets rougher as the engine idles to warm up and condensation builds up.
That’s because condensation means the spark plugs need a stronger spark to ignite the fuel. Luckily, it burns off when you get the engine going. However, if you’re having a rough idle, it likely means it’s time for new spark plugs.
How Do You Replace Spark Plugs? (Video)
In most cases, you can easily change spark plugs yourself. However, you likely want to invest in a spark plug wrench.
In some cases, you can borrow this from your local Autoparts store. However, you can often buy them for $5-$15.
Keep in mind that some vehicles require a deep socket spark plug wrench. Otherwise, replacing spark plugs yourself is a relatively easy job and it shouldn’t take more than a few hours at most.
Things You’ll Need:
- Disposable gloves
- Ratchet and socket set with an extension
- Replacement spark plugs
- Spark plug wrench
- Park your car on a clean and flat surface. Turn off the engine and let it get completely cold. This is important because most cars have aluminum heads and these rip if hot. Make sure you follow safety precautions of taking the key out of the ignition and unplugging the battery from the negative post before you get started.
- Find the wires on the manifold and take them off one at a time.
- Insert the spark plug wrench or a ratchet into the spark plug hole and ratchet it out.
- Inspect the spark plug for damage or oil. If there’s oil on the spark plugs, you likely have valve seal issues as well.
- Use the wrench to insert and screw in the new spark plug.
- Repeat for each cylinder. Your engine has one spark plug per cylinder.
- Make sure you replace the wiring firmly, in the same slot it was in before. For this reason, it’s always a good idea to replace one spark plug at a time and replace the cable as you finish.
Some vehicles have a manifold cap over the spark plug wires. In this case, you can find the bolts and undo them, then simply take it out first.
You might also have to remove the valve cover gasket to access the spark plugs. Here, you want to buy a replacement valve cover gasket as well, because it will not likely re-seal after you take it off.
However, taking it off is a simple matter of undoing a few bolts and pulling the cover off.
If you still have questions about replacing your spark plugs, these questions should help.
Can I replace spark plugs on my own?
Most people can easily replace spark plugs on their own.
In older systems, they often are not covered. In newer systems, you’ll normally have to take the valve cover off first. That might mean buying a new valve gasket.
However, you can usually complete the full job in an hour or two, with no prior experience. At the same time, it’s also crucial that you do not break the spark plugs, as removing a broken spark plug can be extremely difficult.
How long does it take a mechanic to change spark plugs?
Most mechanics can change spark plugs in 30-90 minutes depending on the vehicle.
However, some will charge up to 4 if doing other tasks such as checking the battery, changing the oil, etc.
Replacing spark plugs or replacement spark plugs normally cost around $250 if you buy them from a mechanic. You can often save considerably by choosing aftermarket plugs and doing the work yourself.
However, it’s important that you take care when pulling spark plugs out and when putting new ones in. Otherwise, there’s no reason why you can’t easily replace your own spark plugs.
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