5.7 HEMI Spark Plug Replacement Cost: 16 Plugs, Explained
The HEMI is the one V8 where the plug count drives the bill. Two plugs per cylinder means 16 total, not 8. Here is exactly what that costs, why the interval changed in 2014, and how the price differs between a Ram truck and a Charger.
Quick Answer: 5.7 / 6.4 HEMI
Independent shop pricing. Dealerships run 25-40% higher.
Why the HEMI Has 16 Spark Plugs
The HEMI name comes from its hemispherical combustion chamber. That wide, domed chamber burns well but is hard for a single centrally placed plug to ignite cleanly across the whole charge. Chrysler's answer was two plugs per cylinder: 16 total on an 8-cylinder engine.
A persistent myth says one plug per cylinder is a non-firing spare. It is not. On 2006 and newer engines both plugs fire, sometimes staggered by a few degrees depending on engine load and RPM, to create a faster and more complete burn for better emissions, fuel economy, and smoothness. Because all 16 do real work, they all wear, and the correct service is to replace all 16 as a set. Skipping the second plug per cylinder is not a real cost-saving option.
The cost premium over a regular V8 is almost entirely the plug count. Labor is comparable to other truck V8s because access is similar; you are just buying and installing twice as many plugs.
The 2014 Change: Copper to Iridium
The single most important thing to know before you quote a HEMI plug job is the model year. In 2014 Chrysler switched the 5.7 from copper plugs to iridium and upgraded the coils, which more than tripled the service interval.
| Era | OEM Plug | Interval | 16-Plug Parts | Notes |
|---|---|---|---|---|
| Pre-2014 5.7 HEMI | Copper | ~30,000 mi | $80 - $112 | Cheap plugs, but you replace them three times as often. |
| 2014+ 5.7 HEMI | Iridium | ~100,000 mi | $110 - $160 | Pricier plugs and upgraded coils, far longer interval. |
| 6.4L HEMI (392) | Iridium | ~100,000 mi | $110 - $170 | Found in HD trucks and SRT / Scat Pack cars. |
Always confirm the interval in your owner's manual. Towing, heavy loads, and sustained high RPM shorten plug life on either era.
Cost by HEMI Vehicle
All use the 16-plug layout. The spread is driven by access, not parts. Trucks are easiest; the LX-platform cars (Charger, Challenger, 300) are tightest at the rear bank.
| Vehicle | Engine | Shop Total | DIY | Access Notes |
|---|---|---|---|---|
| Ram 1500 | 5.7L HEMI | $250 - $400 | Moderate | Best access of the group. Longitudinal truck mount reaches all 16 plugs from the top and sides. |
| Ram 2500 / 3500 | 6.4L HEMI | $280 - $450 | Moderate | Same dual-plug layout. Tall engine bay, generally good access. |
| Dodge Charger | 5.7L / 6.4L HEMI | $300 - $450 | Hard | Rear plugs sit near the firewall. More cowl and intake clearance work than a truck. |
| Dodge Challenger | 5.7L / 6.4L HEMI | $300 - $450 | Hard | Similar to the Charger. Tight rear-bank clearance on the car platform. |
| Chrysler 300 | 5.7L HEMI | $300 - $450 | Hard | Shares the LX platform with Charger. Rear plugs are the time sink. |
| Dodge Durango | 5.7L / 6.4L HEMI | $280 - $450 | Moderate | SUV bay gives a bit more room than the sedans. |
| Jeep Grand Cherokee | 5.7L HEMI | $280 - $450 | Moderate | 5.7 variants carry the 16-plug setup; 3.6L V6 variants do not. |
Totals are estimates at an independent shop including parts and labor for all 16 plugs. Dealerships run 25-40% higher. For a full table of non-HEMI vehicles, see cost by car.
Doing It Yourself
A HEMI plug job is one of the more DIY-friendly V8 services, mostly because there is nothing exotic to remove. The catch is patience: 16 plugs, 16 coil or boot connections, and torque that matters.
Budget the time
A Ram 1500 runs about 2 to 3 hours for a first-timer. The LX cars (Charger, Challenger, 300) add time at the rear bank near the firewall.
Torque matters
HEMI heads are aluminum and the plugs are torque-sensitive. Use a torque wrench to the spec in your manual rather than guessing by feel.
Replace all 16
Both plugs per cylinder fire and wear. Do not change only 8. Buy a full set so you are not back in the engine bay in a year.
Anti-seize, carefully
Follow the plug maker's guidance. Many iridium plugs ship pre-coated and need no anti-seize; over-applying can throw off torque readings.
Want the full tool list and torque-spec workflow? See the DIY guide.
Common Questions
How much does a 5.7 HEMI spark plug change cost?
A 5.7 HEMI spark plug replacement runs $250 to $450 at an independent shop. The engine has 16 plugs (two per cylinder), so parts cost $80 to $130 and labor is $100 to $200. Ram trucks have good access and sit at the lower end; Charger and Challenger need more disassembly and run higher.
Why does the 5.7 HEMI have 16 spark plugs?
The HEMI uses two plugs per cylinder because its wide hemispherical chamber is hard for a single plug to ignite cleanly. On 2006 and newer engines both plugs fire, sometimes staggered by load and RPM, for a more complete burn. The non-firing spare idea is a myth, so all 16 are replaced as a set.
How often should you change spark plugs on a 5.7 HEMI?
It depends on the year. Pre-2014 trucks used copper plugs on a roughly 30,000-mile interval. In 2014 the engine moved to iridium plugs with upgraded coils, stretching the interval to roughly 100,000 miles. Confirm against your owner's manual, since towing and heavy use shorten it.
Can you change 5.7 HEMI spark plugs yourself?
Yes. An experienced DIYer can do a Ram 1500 HEMI in about 2 to 3 hours and save $100 to $200 in labor. The truck's longitudinal mount gives decent access to all 16 plugs. Charger, Challenger, and 300 are tighter at the rear bank. Use a torque wrench because HEMI plugs thread into aluminum heads.