01 / THE JOB
What spark plugs do
Each plug fires tens of times per second, jumping thousands of volts across a precisely sized gap to ignite the mixture. Every spark erodes a little electrode metal.
That erosion is the whole story of plug intervals. As the electrodes wear, the gap grows, and the voltage needed to jump it climbs. Eventually the coil cannot reliably light the mixture under load, and the engine misfires, wasting the fuel in that cylinder and sending it into the catalytic converter instead.
Electrode metal determines how fast this happens. Copper electrodes are soft and erode within 30,000 to 40,000 miles. Platinum hardens the tip and stretches life to roughly 60,000 to 100,000. Iridium, harder still, holds a precise gap for 100,000 to 120,000 miles, which is why nearly every modern engine ships with it.
02 / WARNING SIGNS
How worn plugs show up
Random weak sparks show up first at idle, where there is the least momentum to smooth them over.
P0300-series codes mean misfires counted. A flashing check-engine light means stop soon; raw fuel is reaching the converter.
Cold, dense mixtures need the strongest spark. Aged plugs fail here before they fail warm.
Incomplete combustion wastes gasoline gradually, often for tens of thousands of miles before an outright misfire.
A sustained misfire does not just waste fuel; it can overheat and ruin the catalytic converter, turning a plug job into a four-figure exhaust repair.
03 / INTERVAL RANGE
Intervals by plug and engine type
The published number belongs to the engine, not the vehicle. Two trims of the same model can carry different engines with intervals tens of thousands of miles apart.
| Situation | Typical range | What to do |
|---|---|---|
| Copper electrode plugs | 30,000 to 40,000 mi | Mostly older engines and the Hemi V8 |
| Platinum plugs | 60,000 to 100,000 mi | Common on 2000s-era engines |
| Iridium plugs | 100,000 to 120,000 mi | The modern default |
| Small turbo engines | 60,000 mi on some | GM assigns its turbo fours a short clock |
| Heavy towing duty | Inspect early | Pull one plug and read it around 60,000 |
Two outliers deserve a callout. The 5.7L Hemi runs sixteen conventional plugs, two per cylinder, on a 32,000-mile interval, the shortest mainstream schedule in production. And several small turbocharged fours carry 60,000-mile intervals that owners miss because they expect the six-figure norm.
04 / YOUR VEHICLE
Find the interval for your car
The table below shows how the published figure moves across vehicles we cover. Each link opens the full schedule for that year.
| Vehicle | Published interval |
|---|---|
| 2017 Chevrolet Equinox | Every 97,500 mi |
| 2017 Chevrolet Silverado 1500 | Every 97,500 mi |
| 2017 Ford Escape | Every 100,000 mi |
| 2017 Ford F-150 | Every 100,000 mi |
| 2017 Honda Accord | Every 100,000 mi |
| 2017 Honda Civic | Every 100,000 mi |
| 2017 Honda CR-V | Every 100,000 mi |
| 2017 Jeep Grand Cherokee | Every 100,000 mi |
| 2017 Jeep Wrangler | Every 100,000 mi |
| 2017 Nissan Altima | Every 105,000 mi |
| 2017 Nissan Rogue | Every 105,000 mi |
| 2017 Ram 1500 | Every 100,000 mi |
Vehicle intake
Find your schedule
The VIN is usually visible at the base of the windshield.
Sources and review dates appear on every schedule.
05 / DIY OR SHOP
Difficulty depends on the engine bay
On an inline four with coils on top, plugs are an hour of satisfying work. On a V6 mounted sideways, the rear bank hides under the intake plenum, and the job becomes disassembly with plugs at the end. The plug itself is the same; access is everything.
Straightforward on most four-cylinders: cold engine, one cylinder at a time, gap checked, threads started by hand, torqued to spec. Boxer engines and transverse V6 rear banks are honest tests of patience.
Worth the labor on engines requiring intake removal, and any time a plug fights back on the way out. Seized or broken plugs in aluminum heads are shop territory immediately.
06 / COST BREAKDOWN
What replacement costs
Parts are cheap per plug and labor swings wildly with cylinder count and access. Sixteen-plug Hemis and buried V6 banks anchor the high end.
07 / IF YOU WAIT
The cost of running plugs long
Worn plugs tax the car three ways before they ever strand it. They waste fuel through incomplete combustion. They overwork ignition coils, which fail one by one at prices that dwarf the plugs. And a real misfire dumps raw fuel into the catalytic converter, which glows, melts internally, and turns a maintenance skip into an emissions repair measured in four figures.
Against all that, the interval asks very little: one plug service per hundred thousand miles on most modern engines. Put it on the schedule and the ignition system becomes one of the most reliable parts of the car.
08 / QUESTIONS
What owners ask
Why do turbo engines wear plugs faster?
Higher cylinder pressures and temperatures erode electrodes sooner, and some manufacturers assign small turbo engines intervals as short as 60,000 miles even with premium plugs. Towing shortens plug life for the same reason.
Can I upgrade copper plugs to iridium for a longer interval?
Often yes, if an iridium plug exists in the correct heat range and dimensions. Some engines, though, specify copper deliberately, so match the manufacturer listing rather than assuming.
Do worn plugs really damage ignition coils?
Yes. A worn plug's wider gap demands more voltage, which stresses the coil driving it. Coil failures clustered around high plug mileage are common, and coils cost several times what plugs do.
Should all plugs be replaced together?
Always. They wear at the same rate, and labor is the bulk of the job on most engines. Replacing one failed plug on an aged set just schedules the next misfire.
09 / SOURCES
Where to confirm the interval
- 01
The maintenance schedule supplied for your exact model year and engine.
- 02
The owner's manual section covering maintenance and severe-use conditions.
- 03
Service records showing the date, mileage, and parts used at the last service.