How much does it cost to replace spark plugs?

For a four-cylinder engine with coils on top of the plugs and standard copper or iridium plugs, expect $100-$250 total including labour. A V6 with coils integrated into the plug well, or any engine where the intake manifold has to come off to reach the back plugs, runs $300-$500. V8s, coil-pack designs, and luxury badges can reach $600-$800 because access is the labour, not the plugs.

Is it cheaper to replace spark plugs one at a time or all at once?

All at once, always. Since the labour is dominated by the labour rate and the time spent reaching the plugs, changing four of eight plugs gives you half the benefit at close to full cost. The one exception is a single misfire from a failed coil or plug — then you replace only the failed unit to get running, and schedule the rest separately.

How long do iridium and platinum spark plugs last?

Iridium typically lasts 80,000-120,000 miles, and platinum lasts 60,000-100,000. Standard copper is a short-life plug at roughly 30,000 miles. Use the interval your owner's manual specifies for the exact plug, because manufacturers tune the engine management to the plug's service life, and going well past it can cost a catalytic converter.

Is it worth paying a dealer for spark plugs?

The parts are the same price online for OEM-spec plugs, so the dealer's premium is almost entirely labour plus the diagnostic. It is worth paying a dealer if you do not have tools, if the car is still under warranty, or if the engine is a V6 or V8 with buried plugs. For a straightforward four-cylinder, an independent shop should be $40-$80 cheaper on the total.

What are the symptoms of worn spark plugs?

Rough idle, a drop in fuel economy, a misfire that shows up under acceleration, slow starts, and a check-engine light with a misfire code are the usual signals. Failed plugs also often show up as a loss of power at low RPM rather than at highway speed, which is why the problem gets written off as a transmission issue.

Should I replace spark plugs before a road trip?

If the plugs are older than two thirds of their service interval, replace them before a long trip — a misfire miles from anywhere is a much bigger problem than a planned service slot. If they are recent, inspect them instead: pull one plug and look at the electrode wear and the colour of the deposit. Dark, oily deposits mean an oil problem, not a plug problem.

Cost of Spark Plug Replacement in 2026 (By Engine)

At a glance
Total cost runs $100-$250 for a typical four-cylinder and $400-$800 for a V6 or V8 with buried plugs.
The plugs themselves are $6-$25 each. Access is 70-90% of the bill.
Replace them all at once — per-plug pricing means the labour is charged the same either way.
Iridium lasts 80,000-120,000 miles, platinum 60,000-100,000, copper roughly 30,000.
An independent shop beats the dealer by $40-$80 on a straightforward four-cylinder.

Prices last verified October 2026. Parts and labour rates vary by region — confirm current pricing for your vehicle.

Why the parts cost so little and the labour so much

An iridium spark plug is a machined electrode welded to a ceramic insulator with two terminals. It is an extremely well-made component that costs a few dollars in materials. What you pay for is access. Reaching a plug can mean removing the intake manifold, working by feel behind the engine, or unbolting a coil rail that sits under a brace.

This is why quoting a four-cylinder at $500 is not a rip-off to be avoided but a signal that access is difficult. It is also why the labour spread between an independent shop and a dealer on an easy engine is $40-$80, while on a hard engine the spread grows because the independent shops bid less on the same hours.

Engine layout	Typical parts cost	Independent shop labour	Dealer labour	Total at an indie	Total at the dealer
4-cyl, coils on plugs, easy access	$40-$80	$80-$140	$130-$210	$120-$220	$170-$290
4-cyl, coil-on-plug, tight bay	$50-$100	$130-$220	$190-$300	$180-$320	$240-$400
6-cyl, plugs behind intake	$70-$140	$230-$380	$320-$520	$300-$520	$390-$660
8-cyl V8, one side hard	$110-$220	$330-$550	$450-$720	$440-$770	$560-$940
Luxury V6/V8, twin-turbo, coil rail	$150-$320	$480-$800	$650-$1,050	$630-$1,120	$800-$1,370

Copper, iridium, platinum: what the metal actually changes

All three conduct electricity the same way. The difference is erosion rate. A copper electrode wears a visible gap over time, which reduces the energy of the spark at the plug gap. Iridium and platinum are far denser and resist that wear, so the gap stays correct far longer.

The reason to pay for iridium over copper is not performance on day one — it is that the engine's fuel injection and ignition timing were calibrated for a plug that lasts a certain number of miles. Run a cheap copper plug for 150,000 miles and you are running the tune on a worn component.

Plug material	Cost each (2026)	Service life	Gap tolerance	Best for	Weakness
Copper / standard	$5-$9	30,000 miles	Needs frequent checking	Older carburetted engines, low mileage	Erodes fast; re-gap and re-torque often
Platinum	$9-$16	60,000-100,000 miles	Very stable	Turbo engines, stop-start city driving	Costs more than copper for less life than iridium
Iridium / fine-wire platinum	$14-$28	80,000-120,000 miles	Extremely stable	Modern engines, most new vehicles	Can be damaged by excessive gap at install
Double platinum	$18-$32	80,000-120,000 miles	Extremely stable	Direct-injection engines prone to plug fouling	Premium price for a marginal gain

The install mistakes that cost more than the plugs

Re-gapping an iridium plug. Fine-wire iridium is not gapped in a workshop any more. Bending the tiny centre electrode destroys it and the plug must be replaced. If a shop gapped your iridium plugs, that is a mistake worth knowing about.
Omitting the torque spec. Many modern coils use a rubber seal instead of a metal gasket, and those must be installed dry and torqued to spec. Applying anti-seize to a rubber-seal plug welds it into the well and turns a $20 job into a head-removal job.
Mixing plug types across the engine. Even one premium plug among eight standards changes the ignition behaviour slightly and can trigger a misfire code on a sensitive coil-on-plug system.
Ignoring the coil. On a coil-on-plug engine the plug and the coil are one serviceable unit. Replacing the plug alone on a coil that has 80,000 miles on it leaves the most common failure point in place.
Skipping the gap check on a used plug. If you pull a plug to inspect it, measure the gap while it is out. A gap outside spec tells you the plug is finished regardless of what the interval table says.
Not clearing the codes. Old misfire codes sitting in the ECU will keep the check-engine light on after a good repair and can affect how the engine runs until cleared.

Dealer, independent shop, or DIY

The parts are identical wherever you buy them, so the decision is purely about access and risk. DIY makes sense on a four-cylinder where the plugs sit in plain sight and you own a torque wrench. It is a bad idea on anything that needs the intake manifold off, because a stripped bolt or a broken vacuum line costs more than the entire labour quote.

Route	Four-cylinder total	V6/V8 total	Warranty impact	Risk	Best when
Dealership	$170-$290	$560-$1,370	No effect if outside warranty	Lowest	Car is under warranty, or you want OEM parts and a documented service history
Independent shop	$120-$220	$440-$770	None	Low	Default choice — best price-to-quality ratio
Mobile mechanic	$180-$300	$550-$900	None	Low, adds travel fee	No access to a driveway or garage
DIY	$50-$110 (parts + tools)	$120-$350 (parts + tools)	None	High on V6/V8	Four-cylinder with visible plugs and a torque wrench on hand

Two extra line items that catch people: a throttle-body or idle reset is sometimes needed after a service on fuel-injected engines, and many shops will quote an inspection fee of $50-$150 that is waived if you proceed with the work. Ask for the all-in number including both.

The short version

Get iridium plugs unless your manual specifies copper, replace all of them at once, and expect $120-$220 at an independent shop for a four-cylinder or $440-$770 for a V6. Insist on the torque spec, leave the anti-seize alone, and treat a dealer visit as worth it only under warranty or on a genuinely buried engine.

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Written by

Fazlur RahmanAI, Entrepreneurship, EdTech

Fazlur Rahman is the founder of Tutorsbot, building AI-powered tools for learning and career growth. He writes about applying AI in real products and the practi… Read more

Fazlur Rahman is the founder of Tutorsbot, building AI-powered tools for learning and career growth. He writes about applying AI in real products and the practical side of building an ed-tech startup.