A misfire on a 2018 F150 is rarely a catastrophic failure — it is almost always a worn or carbon-fouled spark plug begging for replacement. The real question is whether you install a set that restores factory manners or one that forces you back under the hood within ten thousand miles. The difference comes down to electrode material, gap consistency, and how well the plug tolerates the direct-injection soot that modern EcoBoost and Coyote engines generate.
I’m Amir — the founder and writer behind Four Wheel Ask. My approach to selecting spark plugs involves cross-referencing OEM engineering specs with long-term owner reports across multiple forum communities and verified purchase histories.
Whether you drive a 5.0L V8 or a 3.5L EcoBoost, picking the right best 2018 f150 spark plugs directly affects engine smoothness and long-term reliability.
How To Choose The Best 2018 F150 Spark Plugs
Selecting spark plugs for a 2018 F150 is not a one-size-fits-all task because the truck came with three different engines: the 3.3L V6, the 5.0L Coyote V8, and the 3.5L EcoBoost V6. Each powerplant demands a specific heat range, gap setting, and thread reach. Installing the wrong plug can cause pre-ignition, misfire codes, or even piston damage. The following criteria will help you narrow the field without guesswork.
Electrode Material — Iridium vs. Platinum vs. Copper
Iridium is the gold standard for modern Ford engines because its fine-wire center electrode (typically 0.6 mm) requires lower firing voltage and resists erosion far longer than platinum or copper. A quality iridium plug can reliably last 80,000 to 100,000 miles in a 5.0L or 3.5L, while a copper plug might degrade in half that distance. Platinum offers a decent middle ground but does not match iridium’s longevity under the heat and pressure of a turbocharged EcoBoost.
Gap Consistency and Pre-Gapping
The gap between the center and ground electrode directly dictates whether the spark is strong enough to ignite the air-fuel mixture under load. Many aftermarket plugs ship with gaps that are close but not exact — some reviews confirm gaps ranging from 0.035 to 0.038 inch on plugs labeled for a 0.044-inch spec. Always verify the gap with a feeler gauge before installation. A plug that is 0.005 inch too wide can cause a misfire under heavy throttle.
OE Cross-Reference and Part Number Accuracy
The Ford factory plugs for the 2018 F150 5.0L carry part numbers like SP548 or LTR6AHX. The 3.5L EcoBoost uses LTR6CI-8 or CYFS12YT3. A reputable aftermarket plug will list these exact numbers in its compatibility claim. If the listing only says fits 2018 F150 without specifying the engine or the OE reference, do not trust it. One mismatched thread reach can destroy the cylinder head threads.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Yoshi Motors NGK Iridium IX | Iridium | OE-grade longevity in 3.5L EcoBoost | Set of 6, gap 0.050 in, cross CYFS12YT3 | Amazon |
| ECCPP Coils + Iridium Plugs | Kit | Complete ignition refresh for 5.0L V8 | 7 coils + 7 plugs, UF835, JR3Z-12029-A | Amazon |
| A-Premium Iridium Platinum | Iridium/Platinum | Budget-friendly dual-metal longevity | Set of 8, gap 0.044/0.052 in, 5.0L V8 | Amazon |
| BDFHYK Iridium | Iridium | Entry-level replacement for 5.0L V8 | Set of 8, pre-gapped, cross SP548 | Amazon |
| A-NAFTULY Iridium | Iridium | Budget set for 3.5L EcoBoost | Set of 6, gap 0.032 in, cross 97177 | Amazon |
In-Depth Reviews
1. Yoshi Motors NGK Iridium IX (Set of 6)
This NGK Iridium IX set branded through Yoshi Motors uses the same LTR6CI-8 / CYFS12YT3 cross-reference that Ford specifies for the 3.5L EcoBoost. Multiple customer reports confirm it resolves cylinder 1 misfires where factory plugs had carbon fouling, particularly on 2014-2018 F150s with the twin-turbo V6. The fine-wire iridium electrode reduces the required firing voltage, which is critical on direct-injection engines that coat conventional plugs with soot over time.
Owner feedback on the 3.5L shows consistent smooth idling after installation, with one verified buyer noting that three cracked Motorcraft plugs were replaced without further issues. The gap is listed at 0.050 inch, which aligns with the EcoBoost factory spec. A Raptor owner reported a misfire under 1,000 miles, which suggests that occasional quality variation exists — always check gap before installation regardless of brand reputation.
For daily drivers and tow vehicles running the 3.5L, these plugs strike a strong balance between OE-level construction and a reasonable per-unit cost. The nickel core provides adequate heat dissipation for stock and modestly tuned engines. If you are chasing high boost or E85 fuel, a colder heat-range plug may be necessary, but for 90 percent of owners this set delivers exactly what the engine expects.
What works
- Matches factory cross-reference numbers for 3.5L EcoBoost
- Resolved misfire codes where ignition coil replacement failed
- Smooth idle confirmed on high-mileage examples
What doesn’t
- Gap should be verified — some units vary from spec
- One Raptor owner reported early failure under 1,000 miles
2. ECCPP 7 Ignition Coils with 7 Iridium Spark Plugs
This kit bundles seven ignition coils and seven iridium spark plugs specifically for the 2018-2021 F150 with the 5.0L Coyote V8, covering cylinders 1, 2, and 4 through 8. The coil part number UF835 (also sold as DG565 and JR3Z-12029-A) directly replaces the Ford factory coil. The plug included is iridium, though several verified buyers chose to swap them for NGK Laser Iridium while keeping the coils — a flexible option that points to the coils being the stronger component in this set.
Customer reports on high-mileage trucks — one with 123,000 miles and another with 180,000 miles on a Honda Odyssey — describe complete resolution of hard misfire codes P0301 and P0304 after installation. The coils feature an upgraded copper winding that delivers roughly 15 percent more energy than the factory coil, which helps fire the gap reliably under heavy load. The packaging includes foam inserts that prevent shipping damage, an often-overlooked detail that matters for ceramic insulators.
The most serious negative review describes coil boots failing within a year and fusing to the spark plug, making removal extremely difficult. This risk exists with any aftermarket coil boot that does not use the same silicone compound as OE Motorcraft parts. If you plan to keep the truck beyond 60,000 miles, consider applying dielectric grease to the boot interiors before installation to reduce the chance of corrosion bonding.
What works
- Complete kit eliminates guesswork — coils and plugs match as a system
- Resolved misfire codes on high-mileage 5.0L engines
- Coil design delivers higher energy output than factory spec
What doesn’t
- Coil boots may bond to plugs over time without dielectric grease
- One report of complete boot failure under one year
3. A-Premium Iridium Platinum Spark Plugs (Pack of 8)
A-Premium combines an iridium center electrode tip with a platinum core, a dual-metal design intended to provide the easy firing of iridium with the corrosion resistance of platinum. The set of eight covers the full bank of a 5.0L Coyote V8, and the OE cross-reference includes LTR6IX-11, 6509, 90198, and SP548 — all numbers that align with Ford’s factory plug specifications for the 2011-2017 5.0L and 6.2L engines. The gap is factory-set at 0.044 or 0.052 inch depending on the application.
Buyer feedback on the 5.0L indicates smooth startup and stable idle immediately after installation, with several owners noting that these plugs restored throttle response lost due to high-mileage wear. One verified purchaser used them on a 2016 GMC Acadia 3.6L and found the gaps ranged from 0.035 to 0.038 inch instead of the listed 0.043 inch, requiring re-gapping before installation. This inconsistency suggests batch quality control is not as tight as Motorcraft or NGK, but the plugs functioned correctly after adjustment.
For owners who want a set of eight iridium-compatible plugs without spending per-unit prices that rival premium brands, this pack offers strong value. The manufacturer recommends replacement at 80,000 to 100,000 miles, which matches the factory service interval for the 5.0L Coyote. If you are comfortable verifying and adjusting gaps before installation, this is a solid mid-range choice that covers multiple Ford V8 applications beyond just the F150.
What works
- Dual-metal electrode design for long service life
- Covers multiple Ford V8 applications with one part number
- Restored throttle response on high-mileage 5.0L engines
What doesn’t
- Gap consistency varies between units — re-gapping required
- Not a direct replacement for EcoBoost 3.5L applications
4. BDFHYK Iridium Spark Plug Set of 8
BDFHYK markets this eight-pack as a direct replacement for the 2011-2017 F150 with the 5.0L V8, using the OE cross-reference SP548 and LTR6AHX. The plugs feature an iridium center electrode and isostatic ceramic insulators, which are the same manufacturing methods used by tier-one suppliers. The pre-gapped claim is supported by several verified buyers who reported a perfect fit and immediate smooth operation after installation in their 5.0L trucks.
Owner reports on the 5.0L are uniformly positive across the board — buyers describe the truck running smooth after replacement, with one user noting that carbon-fouled original plugs had caused rough idle and hesitation that disappeared immediately after the swap. The set includes eight plugs, meaning a single purchase covers the entire engine without needing a second box. The one-year warranty provides basic protection against manufacturing defects.
The primary trade-off is the lack of long-term owner data. The brand does not have the decades of fleet validation that NGK or Motorcraft possess, so the 80,000-mile durability claim remains unverified by independent sources. For a budget-conscious owner who plans to sell the truck within 30,000 miles or does not mind replacing plugs again at 50,000 miles, this set performs reliably based on the short-term feedback available. Check the gap before installation, as pre-gapped claims from smaller brands are less consistent than OEM suppliers.
What works
- Eight-pack covers entire 5.0L V8 in one purchase
- Immediate smooth idle and hesitation resolution reported
- OE cross-reference matches factory part numbers
What doesn’t
- Long-term 80,000-mile durability is unverified
- Brand lacks the fleet validation of NGK or Motorcraft
5. A-NAFTULY Iridium Spark Plugs (6 Pack)
A-NAFTULY offers a six-pack of iridium spark plugs that cross-reference to 97177, LTR6CI-8, and CYFS12Y3 — all standard numbers for the 3.5L EcoBoost in the 2011-2019 F150. The 0.6 mm fine-wire iridium tip and laser-welded construction mirror the design approach of premium iridium plugs, and the 0.032-inch gap is pre-set at the factory. The six-pack quantity matches the EcoBoost cylinder count, so no extra plugs go to waste.
Customer reception is mixed. Multiple buyers report that the plugs worked great, with simple installation and immediate improvement in engine smoothness. However, one verified purchase on a 2018 Ford Expedition 3.5L resulted in a check-engine light and misfire code within a month of installation, and the buyer was unable to return the plugs past the 30-day window. This single negative report stands out against several positive ones, but it highlights the variability that can occur with budget-focused brands.
For owners who need a quick set of six plugs for a 3.5L at a minimal upfront cost, this pack is hard to beat on price. The 12-month warranty adds a layer of protection that the negative reviewer did not benefit from due to the return window. If you choose this set, verify the gap before installation and keep the packaging until you have confirmed the engine runs cleanly for at least 500 miles. The risk is low, but the one failure report is worth noting.
What works
- Six-pack matches 3.5L EcoBoost cylinder count exactly
- Fine-wire iridium tip for reliable firing
- 12-month warranty from the seller
What doesn’t
- One verified early failure with misfire code
- Short return window may leave buyers unprotected
Hardware & Specs Guide
Iridium vs. Platinum Electrodes
Iridium has a melting point roughly 700 degrees Celsius higher than platinum, which allows a finer electrode tip — typically 0.6 mm versus 1.1 mm for platinum. The finer tip concentrates the spark energy at a lower voltage, reducing coil strain and providing more consistent ignition under high cylinder pressure. Platinum cores are still used beneath the iridium tip in some designs to improve corrosion resistance and extend service life beyond 80,000 miles.
Gap Specifications for 2018 F150
The 5.0L Coyote V8 requires a gap of 0.052 inch for most 2018 model year builds, though early production 2018 trucks may still use 0.044 inch. The 3.5L EcoBoost uses 0.030 to 0.032 inch depending on the exact calibration. Never assume the plug is pre-gapped correctly — use a wire-type gap tool and adjust gently by prying the ground electrode, never pressing on the center electrode.
Thread Reach and Hex Size
All 2018 F150 engines use a 14 mm thread diameter with a reach of approximately 17.98 mm (0.708 inch). The hex size is 5/8 inch (16 mm). Installing a plug with the wrong reach can cause the electrode to protrude into the combustion chamber and contact the piston, or sit too deep in the cylinder head and foul the threads. Always confirm the reach matches the OE plug before threading by hand.
Torque Specifications
Spark plugs in the 2018 F150 aluminum cylinder head should be torqued to 11-15 lb-ft for the 5.0L and 12-15 lb-ft for the 3.5L. Over-tightening can strip the aluminum threads, leading to a helicoil repair or cylinder head replacement. Under-tightening can cause the plug to loosen over time, allowing combustion gases to leak past the seat and damage the coil boot. Use a torque wrench with a 5/8-inch spark plug socket every time.
FAQ
When should I replace the spark plugs on my 2018 F150?
Can I use the same spark plugs for the 5.0L and 3.5L EcoBoost?
Should I replace ignition coils at the same time as spark plugs?
Are pre-gapped spark plugs reliable enough to install without checking?
Final Thoughts: The Verdict
For most buyers, the best 2018 f150 spark plugs winner is the Yoshi Motors NGK Iridium IX set because it combines the recognized NGK manufacturing quality with accurate cross-referencing for the 3.5L EcoBoost, the engine most prone to carbon-fouling related misfires. If you own a 5.0L Coyote and want a complete refresh, grab the ECCPP coil and plug kit for the convenience of matched components and increased coil energy. And for a straightforward budget replacement on a 5.0L, nothing beats the per-unit cost of the BDFHYK eight-pack.
Certification: BSc in Mechanical Engineering
Education: Mechanical engineer
Lives In: 539 W Commerce St, Dallas, TX 75208, USA
Md Amir is an auto mechanic student and writer with over half a decade of experience in the automotive field. He has worked with top automotive brands such as Lexus, Quantum, and also owns two automotive blogs autocarneed.com and taxiwiz.com.