Spark Plug Replacement Cost for a 2018 Jeep Grand Cherokee

Spark plugs are small parts that do critical work. They ignite the air-fuel mixture in each cylinder, and when they wear out, your engine can misfire, lose power, burn more fuel, or struggle to start. Replacing them on a 2018 Jeep Grand Cherokee is a routine service — but the cost and complexity vary more than most owners expect.

Why the 2018 Grand Cherokee Makes This More Than a Simple Job

The 2018 Grand Cherokee came with three available engines, and that choice matters enormously when estimating replacement cost.

The 5.7L and 6.4L HEMI engines use a dual-plug cylinder head, meaning each cylinder has two spark plugs — eight cylinders, 16 plugs total. That doubles your parts cost and adds significant labor time compared to a typical V8. If you own a HEMI-powered Grand Cherokee and assumed it was a standard 8-plug job, this is the number one thing to understand before you get a quote.

What Drives the Cost Variation

Several factors shape what you'll actually pay:

Plug type. Spark plugs range considerably in price depending on material. Copper plugs are the least expensive but wear faster. Iridium and platinum plugs cost more upfront but are the standard recommendation for modern engines and typically last longer. OEM-spec plugs for the HEMI engines are generally iridium-tipped. Using the correct plug specification matters — the wrong heat range or electrode type can cause problems.

Parts cost alone. For the 3.6L V6, expect to pay for six plugs. For any HEMI engine, budget for 16. Iridium plugs for these engines generally run in the range of $8–$20 per plug at retail, though prices vary by brand, supplier, and region.

Labor. This is where costs diverge significantly by shop. The V6's plugs are reasonably accessible. The HEMI's rear bank plugs — especially on the driver's side — can be awkward to reach, and some shops charge more for the additional access time. Independent shops, dealerships, and chain service centers each have different labor rates. Hourly rates vary widely by geographic area.

Shop type. A dealership will typically charge more per hour than an independent mechanic. A national chain may offer promotional pricing. None of these automatically means better or worse work — it depends on the specific shop.

DIY vs. professional service. Owners with mechanical comfort and the right tools sometimes do this job themselves on the V6. The HEMI is a longer, more involved job. Anyone considering DIY should look up the torque specs and use a torque wrench — over-tightening spark plugs in aluminum heads can cause damage that costs far more to fix.

What to Expect in Total Cost Ranges 🔧

These are general ballpark ranges based on commonly reported figures — actual costs vary by location, shop, and parts selection:

These figures reflect what many owners and shops report — they are not guarantees. Labor rates in high cost-of-living areas, or at dealerships, can push totals higher. Rural independent shops may come in lower.

How Often Spark Plugs Need Replacement

The 2018 Grand Cherokee's service intervals depend on engine and plug type. Iridium plugs, which are factory-installed in most Grand Cherokee trims, are generally rated to last 60,000 to 100,000 miles depending on the manufacturer's specification and driving conditions.

Factors that accelerate wear include frequent short trips, stop-and-go driving, towing heavy loads, and oil consumption issues. A misfiring engine, rough idle, reduced fuel economy, or difficulty starting can all signal that plugs are due — though those symptoms can also point to other issues, which is why a mechanic's diagnosis matters before assuming plugs are the cause.

The Coil-on-Plug Question

Most 2018 Grand Cherokee engines use a coil-on-plug (COP) ignition system, meaning each plug has its own individual ignition coil sitting directly on top of it. When a shop replaces plugs, they'll remove and reinstall these coils. If a coil is damaged or failing, that's an additional cost. Some shops recommend inspecting or replacing coils at the same time as plugs — especially on higher-mileage engines — since labor overlap makes it efficient to address both at once. Whether that makes sense depends on the vehicle's condition and mileage.

What Shapes Your Actual Number

Your final cost comes down to which engine you have, how many miles are on the vehicle, whether any coils or wires need attention, which plug brand and grade you use, where you live, and which shop does the work. The HEMI's 16-plug configuration makes this a meaningfully bigger job than most V8 replacements — that's the piece most owners don't know going in.