Ignition · Spark Plug Intervals
AC Delco Spark Plug Replacement Intervals by GM Engine
GM does not use one spark plug interval across its lineup. A small-block V8 and a turbocharged four-cylinder in the same showroom can be tens of thousands of miles apart, and the difference comes down to the engine, not the badge on the tailgate.
Check Your Engine’s Plug SpecQuick Answer
Under GM’s maintenance schedules for normal driving, the iridium spark plugs in the 5.3L and 6.2L V8s are replaced every 97,500 miles, and GM dealer maintenance schedules list the same 97,500 miles for the 3.6L V6. Several turbocharged engines, including the 2.7L and 1.4L turbos, are on 60,000 miles. Duramax diesels have no spark plugs. Confirm the interval for your model year in the owner’s manual maintenance schedule.
Spark Plug Intervals by GM Engine
| Engine | Common applications | Replace every |
|---|---|---|
| 5.3L V8 | Silverado 1500, Sierra 1500, Tahoe, Suburban, Yukon | 97,500 miles |
| 6.2L V8 | Silverado, Sierra, Tahoe, Yukon, Escalade, Camaro SS | 97,500 miles |
| 3.6L V6 | Traverse, Acadia, Colorado, Canyon, Camaro | 97,500 miles |
| 2.0L Turbo 4-cylinder | Cadillac CT4, CT5, XT4, XT5, XT6; Camaro, Malibu | Varies by model year; see your owner’s manual |
| 2.7L Turbo 4-cylinder | Silverado, Sierra, Colorado, Canyon | 60,000 miles |
| 1.5L Turbo 4-cylinder | Equinox (2018 and later) | Varies by model year; see your owner’s manual |
| 1.4L Turbo 4-cylinder | Cruze and other small Chevrolet models | 60,000 miles |
| Duramax diesel | Silverado HD, Sierra HD and others | No spark plugs |
Sources: the 5.3L, 6.2L and 1.4L turbo figures come from GM owner’s manual maintenance schedules; the 3.6L and 2.7L turbo figures from GM dealer-published maintenance schedules. We could not confirm a GM-sourced figure for the 1.5L turbo or a single figure for the 2.0L turbo across its applications, so we do not state one for either. Intervals can change between model years and engine revisions, so the maintenance schedule in your own owner’s manual is the final word. If your engine is not listed here, the manual or a VIN lookup will give you its interval.
Why the Turbo Engines Come Due Sooner
Turbocharging is what shortens the interval. A turbocharged engine packs more air and fuel into each cylinder, which raises cylinder pressure at the moment the plug fires. Higher pressure takes more voltage to jump the gap, and as the electrodes wear and the gap widens, a turbo engine reaches the point of misfiring under boost sooner than a naturally aspirated V8 would. The shorter interval replaces the plugs before that happens.
97,500
Miles between changes for GM’s small-block V8s.
60,000
Miles for the 2.7L and 1.4L turbo four-cylinders.
8th
VIN character that identifies your GM engine, and so its interval.
When to Change Them Sooner
The intervals above assume normal driving. Some driving patterns wear electrodes faster, and if yours is heavy on any of them, have the plugs inspected before the scheduled mileage rather than waiting for a misfire:
Frequent towing
Sustained load keeps combustion temperatures and pressures high for long stretches.
Short trips
Stop-and-go errands and short commutes on Route 1 traffic keep an engine from reaching full operating temperature, which builds deposits on the plug tips.
Long idling
Hours of idling add wear without adding miles, so the odometer understates how hard the plugs have worked.
Regular E85 use
Flex-fuel engines running mostly E85 see different combustion conditions than on gasoline.
Signs Your Plugs Are Due
Worn plugs rarely fail all at once. They show up as a gradual loss of smoothness: a rougher idle, slightly slower starts, a hesitation when you press the throttle hard, and fuel economy that drifts downward. As wear progresses you may see a random misfire code (P0300) or single-cylinder misfire codes, especially under load or on a turbo engine under boost. In New Jersey that matters beyond drivability: any lit check-engine light fails the OBD inspection for 1996-and-later gasoline vehicles, per NJDEP. A worn plug also makes the ignition coil work harder, which is why a coil failure on a high-mileage engine is often a sign the plugs are overdue too. Our GM ignition components hub covers how to sort a plug problem from a coil, wire or injector problem.
Your Oil Life Monitor Will Not Remind You
GM’s Oil Life System calculates when the oil is due from how the engine is actually used, and many owners treat its reminder as the whole maintenance schedule. It does not track spark plugs. The plug interval is a fixed mileage in the owner’s manual maintenance schedule, so the only way to catch it is to note the odometer at the last change — or, on a used vehicle with unknown history, to treat the plugs as due and read the old ones when they come out.
What the Old Plugs Tell You
A plug that comes out of the engine is a record of how that cylinder has been running. Line the set up in cylinder order before you throw them away:
| Plug condition | What it usually indicates |
|---|---|
| Light tan or gray deposits, rounded electrode | Normal wear; the plug has simply reached its interval |
| Dry black soot | Carbon fouling from a rich mixture, heavy short-trip use or a weak spark |
| Wet, oily deposits | Oil reaching the combustion chamber on that cylinder |
| White, blistered insulator | Overheating, from a lean condition or a plug with the wrong heat range |
| One plug very different from the rest | A problem specific to that cylinder worth diagnosing further |
Replacing Them: What to Know Before You Start
Leave the gap alone
AC Delco iridium plugs for GM engines come pre-gapped to the engine specification. Prying at the fine iridium center electrode with a gap tool can damage it; if you check the gap, use a wire-type gauge and do not bend the center electrode.
Torque to the specification
Plugs are torqued to a specification that varies by engine and is listed in the service information. Too loose risks the plug backing out; too tight can damage the threads in an aluminum cylinder head.
Access varies a lot by engine
On transverse 3.6L V6 applications such as the Traverse and Acadia, the rear bank of plugs sits under the upper intake manifold, which has to come off to reach them. That is a much bigger job than the front three, and worth knowing before you quote yourself an afternoon.
Replace all of them
Plugs are replaced as a full set so every cylinder fires the same way. Inspect coil boots and plug wires while you are there.
Expert Tip: Stay With the Plug GM Specifies
The plug GM specifies for your engine is chosen for its heat range, reach and gap, and on turbo engines those details decide whether the plug lasts to 60,000 miles or starts misfiring under boost well before. Aftermarket “performance” plugs with a different heat range or electrode design do not reliably improve a stock engine and can shorten the interval you are counting on. For the broader case on when original-equipment parts are worth it, see our GM OEM vs aftermarket parts guide.
The Right Plugs for Your Engine Code
Plug numbers differ even between engines of the same size, so we start from the VIN. Send us yours and our North Brunswick parts counter will confirm the engine, the AC Delco plug it specifies, and whether coils, wires or boots are worth adding to the order.
Ask a Parts Expert Which Plugs You NeedSpark Plug Interval FAQ
How often should AC Delco spark plugs be replaced on a GM vehicle?
It depends on the engine. GM’s 5.3L and 6.2L V8s are on a 97,500-mile interval, GM dealer schedules list 97,500 miles for the 3.6L V6, and turbo four-cylinders such as the 2.7L and 1.4L are on 60,000 miles. Check your owner’s manual for your model year.
How often do you change spark plugs on a Silverado with the 5.3L?
GM’s maintenance schedule calls for replacing the iridium spark plugs in the 5.3L V8 every 97,500 miles under normal driving.
Why do turbo engines need spark plugs more often?
Turbocharging raises cylinder pressure, which takes more voltage to fire the plug. As the gap wears wider, a turbo engine starts misfiring under boost sooner, so GM specifies a shorter interval.
Does a Duramax diesel have spark plugs?
No. A diesel ignites fuel by compression and uses glow plugs to help cold starts, so it has no spark plugs to replace.
Do I need to gap new AC Delco iridium spark plugs?
AC Delco iridium plugs for GM engines come pre-gapped. If you check the gap, use a wire-type gauge and avoid bending or prying the fine center electrode.
What are the signs spark plugs need replacing?
Rough idle, slower starts, hesitation under hard acceleration, falling fuel economy and misfire codes, especially under load, are the common signs of worn plugs.