Spark plug replacement costs $100 to $430 as a national range, and CarMD’s 2025 average is $299, or $480 when the ignition coils are replaced too. A four-cylinder with the plugs on top sits near the bottom of that range. A V6 with plugs under the intake, or a set of iridium plugs, sits near the top. Blue Rose Auto replaces spark plugs and diagnoses misfires for drivers in Eugene and Springfield, Oregon, and we quote after diagnosis. The first 15 minutes are free, and you can reach us at (541) 641-8877. The figures below match what common repairs cost in national data, and the plug interval depends on your engine. Plugs usually land in the 60,000-mile service, but your owner’s manual wins.
Last updated October 2026
Key takeaways
- Spark plugs run $100 to $430 as a national range. CarMD’s 2025 average is $299, or $480 when the ignition coils are replaced too.
- Labor drives the spread more than parts. A V6 with the rear bank under the intake plenum takes longer than a four-cylinder with plugs in a row on top.
- Plug metal sets the interval. Bumper lists copper at 20,000 to 30,000 miles and iridium at 60,000 to 120,000, and NGK says the maker’s schedule decides.
- A flashing check engine light means stop driving, because a severe misfire can damage the catalytic converter.
Why Spark Plug Replacement Cost Is Different for Every Vehicle
NGK, a plug maker, gives no single replacement interval, because engine condition, correct installation and the electrode metal all change how long a plug lasts. The same three things change the bill. We price each job around where the plugs sit, which plug the engine takes, and how the car is driven.
- Engine layout. Plugs in a row on top of the head come out in minutes. Plugs buried under the intake or behind brackets add labor.
- Plug type. Copper plugs cost less per plug and wear sooner. Platinum and iridium cost more and last longer.
- Driving. Short trips and long idling can build carbon on a plug, and NGK lists carbon build-up as a cause of plug failure.
- Condition of the parts around the plugs. Cracked coil boots, oil in the plug wells and seized plugs all add time.
Honda Accord and Toyota owners ask us about cost by model all the time. The model matters less than the engine under the hood, so we put each car in the engine table further down and quote after we confirm the plug type.
Spark Plug Replacement Cost at a Glance
The national range for a spark plug job is $100 to $430, with a CarMD 2025 average of $299 and $480 when ignition coils are replaced too. The chart plots those three figures on one scale, with markers reading CarMD average, $299 and CarMD average with coils, $480 against the National range bar of $100 to $430. The table spells out where each number comes from.
| What we are pricing | Figure | Where it comes from |
|---|---|---|
| Spark plug replacement, national range | $100 to $430 | National range |
| Average spark plug replacement | $299 | CarMD 2025 average |
| Plugs and ignition coils replaced together | $480 | CarMD 2025 average |
| Most four-cylinder engines | $100 to $250 | Published estimate, Bumper 2026 |
| Most V6 and V8 engines | $150 to $400 and up | Published estimate, Bumper 2026 |
| Blue Rose Auto | Quoted after diagnosis | First 15 minutes free, then $100 an hour, credited to an approved repair |
The Bumper rows are a published estimate, not a Blue Rose Auto price list. We do not post a flat spark plug price, because the plug, the engine and the parts around it change the job. We look at the car, tell you the plug type and the labor involved, and you approve the work before we start.
What a Spark Plug Does and When It Wears Out
A spark plug is the part that lights the fuel and air mixture in each cylinder. The ignition coil builds up to 40,000 volts according to Bumper, and the plug fires that voltage across a small gap, which starts combustion. Every time the plug fires, the electrode wears a little and the gap widens.
A wider gap asks more of the coil and weakens the spark. NGK lists the causes of plug failure as age, carbon build-up, overheating, oil in the combustion chamber and an incorrect gap. The first one is the one we see most. An old plug that ran past its interval is cheap to replace compared with the parts it stresses on the way out.
Replacement timing comes from your manual. Spark plugs usually appear in the 60,000-mile service of the 30-60-90 schedule, but Jalopnik reports that some manufacturers now rate plugs to 120,000 miles. A plug change that once sat at 60,000 can move out on a newer car, and that is why we read the manual before we quote.
Spark Plug Replacement Cost for a 4-Cylinder, V6 and V8
A four-cylinder plug job costs $100 to $250 and a V6 or V8 job costs $150 to $400 and up, according to Bumper’s April 2026 estimates. The gap is labor. Plug access changes with the engine layout, and access is the single biggest reason a quote moves.
| Engine layout | Plug access | Labor | Published estimate | Watch for |
|---|---|---|---|---|
| Four-cylinder | Plugs on top | Under an hour for most | $100 to $250 | Coil boots |
| Transverse V6 | Rear bank under the intake | Plenum removed, new gasket | $150 to $400 and up | Intake gasket |
| V8 | Both sides, low | Brackets and wiring in the way | $150 to $400 and up | Coils and wiring |
| Turbocharged four or six | Tight spaces around the turbo and intake | Clearance and parts removed | Quoted after inspection | Tight clearances |
Estimates are from Bumper, April 2026, along with the access notes from the same page. They are not a Blue Rose Auto price list. A Honda Accord with the four-cylinder engine belongs in the first row, and an Accord with a V6 belongs in the second. Toyota builds four-cylinders, V6 engines and V8 engines, so a Toyota’s row depends on the engine and not the badge.
Four-cylinder engines
Most four-cylinders carry the plugs in one row on top of the head, each under its own coil. Bumper puts a full iridium set at $40 to $80 in parts and under an hour of work on most of these engines. That is why the four-cylinder quote sits near the bottom of the range. Our own attention goes to the coil boots, which can crack or stick to the plug as they age.
Transverse V6 and the rear bank
A transverse V6 sits sideways in the engine bay, so one bank of plugs faces the radiator and the other faces the firewall. The front bank is easy. The rear bank sits under the upper intake plenum, and Bumper notes the plenum can need to come off to reach those plugs. We take the plenum off, replace the plugs and fit a new intake gasket as standard practice. That extra work is most of the difference between a four-cylinder bill and a V6 bill.
V8 and turbocharged engines
V8 plugs sit low on both sides of the engine near the manifolds, with coils, brackets and wiring in the way. Turbocharged engines pack the turbo and intake into tight clearances, and Bumper lists them with the jobs that need parts removed first. We inspect a V8 or turbo engine before we give a number, because the same engine can be easy or slow depending on what is bolted around it.
Copper, Platinum and Iridium Plugs and How Long Each Lasts
Copper plugs last 20,000 to 30,000 miles, platinum 60,000 to 100,000 and iridium 60,000 to 120,000, according to Bumper’s April 2026 figures. The metal sets the interval and the price per plug, so the cheapest plug is rarely the cheapest job over the life of the car.
| Plug type | Typical life | Typical cost per plug |
|---|---|---|
| Copper (nickel alloy) | 20,000 to 30,000 miles | $3 to $8 |
| Platinum | 60,000 to 100,000 miles | $8 to $20 |
| Iridium | 60,000 to 120,000 miles | $10 to $30 |
Mileage and prices are from Bumper, April 2026. NGK says there is no single interval. Your owner’s manual sets the real interval, and we follow it. NGK describes its standard plugs as nickel alloy with a copper core, and it says its iridium and platinum plugs give longer replacement intervals.
Never downgrade the plug to save money. Bumper warns against swapping iridium for copper to save about $5 a plug, because the copper plug wears out much sooner and you pay for the labor twice. If your car came with iridium, we put iridium back in. If it came with copper and you want a longer interval, we check what the maker allows before we change the metal.
Spark Plug Replacement Cost and Common Signs It Is Due
The common signs of worn spark plugs are reduced fuel economy, rough idling, engine misfiring and hard starting, all of which NGK lists. A car with worn plugs rarely fails all at once. It gets a little worse each month, which makes the early signs easy to dismiss.
- Hard starts on cool mornings. Worn plugs struggle to light the mixture when the engine is cold.
- Rough idle at a stoplight. One or more cylinders are firing unevenly, and you feel it in the steering wheel and seat.
- Hesitation when you accelerate. Merging or climbing a grade feels flat because a cylinder is not contributing.
- Fuel mileage that slips with no other cause. Incomplete combustion wastes fuel on every drive.
- A check engine light. A steady light with a misfire code means a cylinder has been missing, and a flashing light means stop driving.
These symptoms overlap with other problems, so we confirm before we replace anything. If the whole engine feels off and the plugs are only one item on the list, a full tune-up may be the better conversation. If the plugs are the problem, replacing them on time is the cheapest repair on this page.
Misfire Codes (P0300 and P0301 to P0312) and What They Mean for Cost
A P0300 code means the engine control module detected a random or multiple-cylinder misfire, and P0301 to P0312 point to a single cylinder, with the last digit naming it. The code names the cylinder, not the cause. A bad plug is the most common cause, but a coil, an injector or low compression can set the same code.
The strip below reads P0300 random misfire, P0301 cylinder 1, P0302 cylinder 2, P0303 cylinder 3, P0304 cylinder 4, and P0306 cylinder 6, P0308 cylinder 8 for the larger engines.
| Code | What it means | What we do first |
|---|---|---|
| P0300 | Random or more than one cylinder misfiring | Check plugs and coils on every cylinder, then fuel and air |
| P0301 | Cylinder 1 misfiring | Look at that cylinder’s plug and coil first |
| P0302 to P0312 | Cylinder 2 to cylinder 12, last digit is the cylinder | Same check on the named cylinder |
| Flashing check engine light | Severe misfire in progress | Stop driving and call us |
Where cylinder 1 sits depends on the make, so we look it up in the service information for your engine instead of guessing. Our order is simple. Read the code. Check plug and coil on that cylinder. Test fuel and compression if the plug and coil are fine. We run the diagnosis and read the codes at our shop in Springfield. The first 15 minutes are free, then $100 an hour, and that time is credited to an approved repair.
Plug or coil
When a code points to one cylinder, we check that cylinder’s plug and then its coil. If the plug looks worn, we replace the set. If the plug looks fine, we move the coil to another cylinder, clear the codes and see whether the misfire follows the coil. A misfire that follows the coil means a bad coil, and one that stays means we keep looking at the injector, the compression and the fuel and air. That test costs a little time and saves you from buying a coil you did not need.
Why a flashing light means stop
A flashing check engine light means stop driving, because it signals a severe misfire. Bumper notes that a single misfiring cylinder can damage the catalytic converter if the misfire is severe and sustained, because unburned fuel reaches the converter. A catalytic converter costs $1,300 to $3,500 nationally to replace, according to the repair cost guide. Parking the car and calling costs far less than driving it home.
Coil-on-Plug, Ignition Coils and Spark Plug Wires
Most modern engines use coil-on-plug ignition, with one coil sitting directly on each spark plug. Older engines use a distributor or a coil pack with spark plug wires carrying the voltage to each plug. Both setups end with the same plug in the same combustion chamber, but the parts we check around it are different.
With coil-on-plug, a worn plug makes its coil work harder, and a coil that has been stressed for a long time can fail. That is why CarMD’s 2025 average rises from $299 to $480 when coils are replaced at the same visit. We do not replace coils by default. We test them, so you pay for a coil only when it is bad.
The cost to replace spark plugs and wires on an older car runs higher than a plug-only job, because the wires are another part and another set of connections. We quote the wires with the plugs after we inspect them, and we do not guess a price from the model year. Cracked insulation, burned boots and corrosion at the terminals tell us whether the wires are worth replacing now. Replacing aging wires together with the plugs can spare you a second visit on an older daily driver.
What Is Included When We Replace Spark Plugs
A spark plug job at Blue Rose Auto covers more than removing old plugs and installing new ones. The steps below are our standard process, and your car’s engine decides the details.
- We confirm the plug type and gap your engine calls for.
- We let the engine cool, because Bumper recommends about two hours before pulling plugs from an aluminum head.
- We remove the coils or wires, clean the plug wells and pull the old plugs.
- We read the old plugs, because the deposits and electrode wear tell us about combustion in each cylinder.
- We check the gap and install the new plugs with a torque wrench to specification, which matters in an aluminum head.
- We check the coil boots or wires, refit everything, clear any codes and road test the car.
A weak battery can mimic a hard-start problem, so when starting is the complaint we also test the battery and charging system during diagnosis. Our work is covered by a 3-year, 36,000-mile warranty on mechanical repairs. Diagnosis starts with 15 free minutes, then runs $100 an hour, credited to an approved repair.
Spark Plug Replacement Cost and Fuel Mileage
Worn plugs can lower fuel economy, which NGK lists as a symptom, because an incomplete burn wastes fuel. New plugs on an engine that was misfiring can bring mileage back toward normal. We do not put a dollar figure on the savings, since it depends on the car and how it is driven. Treat better mileage as a possible bonus and not as the reason to replace the plugs.
Spark Plug Service for Eugene and Springfield Drivers
Blue Rose Auto serves Eugene and Springfield drivers from 3436 Olympic St in Springfield, about 7 miles and 15 minutes from downtown Eugene via I-105. If most of your driving is short trips around town, check the plugs at the early end of your manual’s range. NGK lists carbon build-up as a cause of plug failure, and short trips and long idling are how carbon builds.
Drivers who work with an Eugene auto repair team on routine maintenance can bring the plug question to the same visit. We also handle plug jobs for customers who come in with a rough idle or a check engine light from our Springfield shop.
Common Misunderstandings About Spark Plug Replacement
- All plugs are the same. They are not. The metal, the gap and the heat range are matched to the engine, and the wrong plug can cause misfires.
- Replace only the plug that misfires. We replace the full set, because the plugs wear at the same rate and the labor overlaps. Replacing one cylinder’s plug means paying for the same access again later.
- A code means a new plug. A misfire code names a cylinder, and the cause can be the plug, the coil, an injector or low compression.
- Long-life plugs never need checking. Even an iridium plug can foul, and NGK lists oil in the chamber and an incorrect gap among the causes of failure.
- The cheapest plug saves money. It saves about $5 a plug and shortens the interval, which costs more in labor over time.
Frequently Asked Questions About Spark Plug Replacement Cost
How much does spark plug replacement cost?
Nationally it runs $100 to $430, and CarMD’s 2025 average is $299. The total climbs to about $480 when ignition coils are replaced at the same visit. A V6 with plugs under the intake costs more than a four-cylinder with plugs on top. We quote after diagnosis, and the first 15 minutes are free.
How much does it cost to replace spark plugs on a 4-cylinder?
Bumper’s 2026 estimate for most four-cylinders is $100 to $250 for parts and labor, with the plugs on top and usually under an hour of work. Iridium plugs cost more per plug but last longer. We confirm the plug type and the price before the work starts.
Why do V6 engines cost more to do?
On a transverse V6 the rear bank sits under the upper intake plenum, so the plenum has to come off to reach those plugs. That adds labor and usually a new intake gasket. Bumper puts V6 and V8 jobs at $150 to $400 and up, against $100 to $250 for most four-cylinders.
How often should spark plugs be replaced?
It depends on the plug and the engine, and NGK says there is no single interval. As a rough guide from Bumper, copper lasts 20,000 to 30,000 miles, platinum 60,000 to 100,000 and iridium 60,000 to 120,000. Follow your owner’s manual first, because some makers now rate plugs to 120,000 miles.
What are the signs of bad spark plugs?
NGK lists reduced fuel economy, rough idle, engine misfiring and hard starting. You may also feel hesitation when you accelerate. If the check engine light flashes, stop driving, because a severe misfire can damage the catalytic converter. A steady light and a rough idle are worth a diagnosis before the problem grows.
What does a P0300 or P0301 code mean?
P0300 means a random or multiple-cylinder misfire. P0301 means cylinder 1, P0302 cylinder 2, and so on, with the last digit naming the cylinder. The code names the cylinder, not the cause. We check the plug and coil on that cylinder first, then fuel and compression if both are fine.
Should I replace spark plugs and ignition coils together?
Only when a coil has failed or the plugs are worn enough to have stressed it. CarMD’s 2025 averages are $299 for plugs and $480 when coils are replaced too. We test the coil, so you pay for a coil only if it is bad, and we do not add one to the quote by default.
Is it worth paying for iridium plugs?
If your car came with iridium, yes. Bumper’s figures put iridium at $10 to $30 per plug and 60,000 to 120,000 miles, against 20,000 to 30,000 for copper. Putting copper in an engine built for iridium saves about $5 a plug and shortens the interval, so you pay for the labor again sooner.
Can bad spark plugs hurt the catalytic converter?
Yes, if a misfire is severe and lasts. Unburned fuel reaches the converter, which costs $1,300 to $3,500 nationally to replace. A flashing check engine light is the warning. Catching a worn plug early costs a small fraction of that, and the converter is the part worth protecting.
Do spark plugs wear out faster in short city trips?
Short trips and long idling can build carbon on a plug, and NGK lists carbon build-up as a cause of plug failure. If most of your driving in Eugene and Springfield is short trips, check the plugs at the early end of your owner’s manual range. Steady highway miles are easier on them.
Book Spark Plug Service at Blue Rose Auto
If your car idles rough, starts hard or has a check engine light, bring it to 3436 Olympic St in Springfield and we will read the codes and look at the plugs. Call (541) 641-8877 or send us a message, and we quote after diagnosis. The first 15 minutes are free, then $100 an hour, credited to an approved repair.
Sources
- CarMD, Vehicle Health Index, April 2026 (2025 average repair costs)
- Bumper, Changing Spark Plugs, April 30, 2026
- NGK Spark Plug Europe, You asked Google and NGK Spark Plug answers, Part 1, October 2021
- Jalopnik, Does the 30-60-90 rule for car maintenance actually make sense
- Blue Rose Auto, repair cost guide (national ranges for spark plugs and catalytic converters)
0 Comments