Related Maintenance
What Else to Replace When Changing Spark Plugs
If you are already paying for spark plug labor (or doing the work yourself), some items cost very little extra to address at the same time. Others are upsells you can skip.
Updated April 2026
Related Items Checklist
| Item | Parts Cost | Shop Labor | Interval | Replace Now? |
|---|---|---|---|---|
| Ignition coils | $20-$80 each | $0-$30 (overlaps with plug labor) | Only if failing | If cracked or failing |
| Spark plug wires (if equipped) | $30-$80 set | $0-$20 (trivial labor) | 80,000-100,000 mi | If brittle or cracked |
| Engine air filter | $10-$25 | $0 (30-second job) | 15,000-30,000 mi | Easy win |
| PCV valve | $10-$20 | $0-$15 (5-minute job) | 30,000-60,000 mi | Cheap insurance |
| Dielectric grease | $4-$6 | N/A (apply to coil boots) | Every plug change | Always |
Ignition Coils: When to Replace
Symptoms of a Failing Coil
A failing ignition coil produces symptoms identical to a bad spark plug: rough idle, misfires, check engine light with P030X codes, and poor fuel economy. The diagnostic challenge is telling them apart.
How to test
Swap the coil from the misfiring cylinder with a coil from a known-good cylinder. Clear the code and drive. If the misfire follows the coil to the new cylinder, the coil is bad. If the misfire stays on the original cylinder, the spark plug (or injector) is the problem.
Replace All or Just One?
This is debatable. The argument for replacing all coils: if one has failed at 100,000 miles, the others are running on borrowed time. They experienced the same heat cycles and are the same age.
The argument against: coils do not have a predictable lifespan like spark plugs. One may fail at 80,000, another at 150,000. Replacing four good coils preventively costs $80-$320 for no immediate benefit.
Practical guidance
Replace the failed coil. Visually inspect the others for cracked boots (the rubber that seals against the plug). Replace any with visible cracks. Keep the old working coils as spares in the trunk.
Cost context: Aftermarket coils run $20-$80 each depending on the brand and vehicle. OEM coils from the dealer cost $40-$120 each. For most vehicles, aftermarket coils from reputable brands (Delphi, Spectra, Standard Motor Products) perform identically to OEM.
Spark Plug Wires
Most cars made after approximately 2005 use coil-on-plug ignition, where each coil sits directly on the spark plug. These cars have no spark plug wires. If your car is newer and you see individual coils (rectangular connectors) sitting on top of each plug, you do not have wires and can skip this section.
If your car has a single coil pack or distributor with wires running to each spark plug, those wires deteriorate with heat and age. Cracked, brittle, or arcing wires cause the same symptoms as bad spark plugs. A wire set costs $30-$80 and takes 15-20 minutes to replace.
How to check
Look at the wires with the engine running in a dark garage (turn off the lights). Arcing wires will show visible sparks jumping from cracks in the insulation. Also feel the wires. If they are stiff, cracked, or the rubber crumbles when you bend them, replace the set.
What a "Tune-Up" Actually Includes in 2026
Modern Tune-Up (What You Actually Get)
Old-School Tune-Up (What It Used to Mean)
Before electronic ignition (pre-1980s), a tune-up included:
- -Points and condenser replacement
- -Distributor cap and rotor replacement
- -Timing adjustment with a timing light
- -Carburetor adjustment
- -Spark plug replacement
None of these components exist on modern cars. If a shop quotes you for a "tune-up," ask exactly what is included. The word has no standardized meaning in 2026.
What to Skip
These are commonly offered alongside spark plug work. Most can be deferred or done cheaply yourself.
Fuel system cleaning
Skip it$100-$200
Modern gasoline already contains detergent additives required by the EPA since 1995. Unless you have specific symptoms (hesitation, rough running, confirmed dirty injectors), this is an upsell. If you want to try it, a $5-$15 fuel injector cleaner additive (Chevron Techron, Gumout) does a similar job run through a tank of gas.
Throttle body cleaning
Easy DIY if needed$80-$150
If you have rough idle or stalling, a dirty throttle body can be the cause. But this is a 15-minute DIY job with a $6 can of throttle body cleaner and a rag. Remove the air intake hose, spray and wipe, reconnect. Do not pay $150 for this.
Fuel injector cleaning service
Rarely needed$80-$200
Different from fuel system cleaning. This is a pressurized cleaning service that runs solvent through the fuel rail. Legitimate if you have confirmed clogged injectors (fuel trim data showing lean on specific cylinders). Rarely necessary on cars that use quality fuel.
Engine air filter (at shop markup)
Buy yourself for $10-$15$30-$50 installed
Air filters cost $10-$25 at an auto parts store and take 30 seconds to swap. The shop is charging $15-$35 for labor on a job that involves unclipping two latches. Buy it from the store and change it yourself.
Cabin air filter (at shop markup)
Buy yourself for $10-$20$40-$70 installed
Not related to engine performance at all. Filters the air coming through your vents. Usually behind the glove box. Takes 5 minutes to replace. The part costs $10-$20. Do not pay $70 for this.
Coolant flush
Separate maintenance item$100-$200
Coolant should be flushed every 30,000-50,000 miles or per your manual. It is legitimate maintenance but has nothing to do with spark plugs. If the shop bundles it, make sure you actually need it based on your mileage and last flush date.