The best spark plugs for a 5.7 Hemi are the exact OE-specified plugs, or a manufacturer-cataloged equivalent, for your vehicle’s year, model and engine. Start with a VIN-based Mopar lookup. NGK Laser Iridium 92145, NGK standard 92174 and NGK Iridium IX 4469 are useful parts to compare for specific applications, but none should be ordered simply because a listing says “5.7 Hemi.”
This guide explains the meaningful differences, how to check fit and how to avoid buying the wrong quantity. It covers stock gasoline engines; modified engines, engine swaps and alternative-fuel applications need their own specifications.
Reviewed October 4, 2026. This is a manufacturer-documentation buying guide, not a hands-on test. As an Amazon Associate, we earn from qualifying purchases. Product links do not determine our recommendations.
Quick comparison: which spark plug should you investigate?
The vehicle examples below come from NGK’s 2019 North American application catalog, (Ram, printed page 222). They are examples, not a complete or current fitment list. Recheck any choice in the current NGK Part Finder and your vehicle’s service information before purchase.
| Option | Useful starting point | Main limitation |
|---|---|---|
| Mopar OE, exact VIN-matched part | Owners who want the vehicle manufacturer’s specified service replacement | There is more than one Mopar part; confirm the full number and any supersession |
| NGK Laser Iridium 92145 / LZFR5CI-11 | Catalog OE-column example: 2014–2017 Ram 1500, 5.7L V8 | Do not extend this example to every Hemi, fuel type or later model year |
| NGK standard 92174 / LZFR5C-11 | Catalog OE-column example: 2011–2013 Ram 1500, 5.7L V8 | Standard and Laser Iridium parts have similar-looking names but different construction |
| NGK Iridium IX 4469 / LFR5AIX-11 | Listed aftermarket alternative for the above Ram applications in that catalog | Iridium IX and Laser Iridium do not have the same service-life specification |
1. VIN-matched Mopar: our default starting point
For a stock vehicle, our first recommendation is to establish the current Mopar service part before comparing alternatives. The official listing for SP143877AB identifies 5.7L Hemi engine applications and says it replaces 68143877AB and SP143877AA. Mopar also maintains a separate SPLZFR5C11 listing. These numbers should not be treated as interchangeable on the strength of a broad product title.
Why choose this route: it gives you a specific OE reference to check against the vehicle, the invoice and any aftermarket cross-reference. Ask the dealer or qualified parts supplier to confirm the number using the VIN, including production details that a generic year-and-engine search may miss.
Trade-off: a Mopar-branded listing alone does not establish that it fits your vehicle. Verify whether the quoted price is for one plug or a package, and compare the total required quantity rather than the first price on the page.
2. NGK Laser Iridium 92145: an OE-style choice where specified
The identifying details are stock number 92145 and part number LZFR5CI-11. Keep the “I” in the part number: LZFR5C-11 is a different plug.
NGK explains that its OE Iridium design uses iridium at the center tip and platinum at the ground electrode. The two precious-metal surfaces are intended for longevity. That makes Laser Iridium a sensible comparison when your vehicle’s current application lookup specifies it. It is not a reason to change the prescribed heat range or assume that every iridium plug is equivalent. See NGK’s explanation of OE Iridium and Iridium IX.
Choose it when: NGK’s current catalog confirms this exact number for your vehicle and it meets the required service specification. Check first: the full part number, quantity and seller; we have not verified an Amazon listing for this option. Check NGK fitment.
3. NGK standard 92174: retain the specified standard design
Stock number 92174 is LZFR5C-11. It is worth checking when you are replacing an application specified for that standard plug rather than selecting a more expensive material by default.
“Copper plug” is common shopping shorthand, but it can be misleading. NGK says standard plugs use a nickel-alloy electrode; copper is generally part of the internal core, and precious-metal plugs can also have copper cores. The label “copper core” therefore cannot tell you whether two plugs are equivalent. See NGK’s spark-plug technical guidance.
Choose it when: the exact application calls for it. Limitation: do not assign it the maintenance interval of an iridium-equipped vehicle. Use the vehicle-specific schedule and any applicable service updates. Check NGK fitment.
4. NGK Iridium IX 4469: a catalog-listed alternative to evaluate
The full part number is LFR5AIX-11. NGK describes Iridium IX as a single-precious-metal aftermarket design and distinguishes its service interval from the dual-precious-metal Laser series. A listing that says only “NGK iridium” leaves out an important difference. Do not assume the original long-life interval carries over after a substitution. Compare the two NGK iridium families.
The Amazon listing linked below was verified as an eight-pack of NGK 4469 / LFR5AIX-11. That establishes the listing’s identity, not fitment, authenticity of every seller’s stock or current availability. An eight-pack is only half of a 16-plug service.
NGK (4469) LFR5AIX-11 Iridium IX Spark Plug (8 Pack) | Replaces MZ602090 BY481-LFR5A 4703 5343 5617 IKH16 VKH16 IKH16TT 9609 FR8MII33X 7975 XP5325 XP5325DP2. 40k-60k mileage.
As an Amazon Associate we earn from qualifying purchases.
Choose it when: the current catalog lists it for your exact vehicle and you have confirmed an appropriate replacement schedule. For an uncomplicated OE-equivalent service, establish the original specification first.
How to buy the correct set
- Identify the vehicle precisely. Record the year, make, model, engine and VIN. Tell the supplier about engine swaps, tuning, forced induction or alternative fuel rather than relying on the badge on the body.
- Find the OE specification. Use the owner’s manual and a current vehicle-specific parts lookup. Resolve conflicting recommendations with the vehicle or plug manufacturer before ordering.
- Match the whole part number. Small changes in letters or suffixes can identify a different product. A matching thread size or similar photograph is not a complete compatibility check.
- Count actual plugs. The cataloged 5.7L Ram examples above require 16. Check whether the listing is a single plug, four-pack, eight-pack or complete set.
- Compare the complete service cost. Include the required quantity and installation quote. A cheaper pack that changes the service interval may be a poor fit for your maintenance priorities.
Gap, installation and replacement intervals
Use the specification for the exact engine and plug. For example, the 2013 Ram 1500/2500/3500 owner’s manual gives a 0.043-inch (1.1 mm) gap for its 5.7L engine. That is a documented example, not a universal gap instruction. A retailer’s “pre-gapped” description does not replace checking the applicable specification.
NGK warns that incorrect torque can damage plugs or the engine, advises against anti-seize on its plated spark-plug threads, and cautions against damaging fine-wire electrodes during gap checks. Have a qualified technician follow the vehicle service procedure and plug manufacturer’s instructions; this guide does not supply a universal torque value or installation procedure. Read NGK’s installation cautions.
Replacement timing also changes by application. The 2013 Ram 1500/2500/3500 owner’s manual shows 30,000-mile replacement increments in its 5.7L schedule. The 2014 Ram 1500/2500/3500 owner’s manual places its 5.7L replacement at 100,000 miles. Both identify spark-plug timing as mileage-based. These examples demonstrate why a single “Hemi interval” is unreliable; follow your own manual and applicable service guidance.
Frequently asked questions
How many spark plugs does a 5.7 Hemi need?
The 5.7L Ram applications discussed here use two plugs per cylinder, 16 total. Confirm the exact engine and package quantity before buying; an eight-cylinder label on a set does not necessarily mean it contains 16 plugs.
Are iridium plugs always better than standard plugs?
They are not automatically the right replacement. Material, application approval and the intended maintenance schedule all matter. Start with the required specification, then compare approved options. Do not downgrade a prescribed long-life design merely to save on the purchase price.
Will new plugs add horsepower or improve fuel economy?
We have no vehicle-specific test results supporting a horsepower or fuel-economy gain for these recommendations. Treat them as maintenance choices. If the engine runs poorly, have the cause diagnosed rather than assuming a premium plug will solve it.
What about older Hemis or modified engines?
The example table does not establish fit for early production years, engine conversions or modified engines. Use the specific engine’s service information and get the engine builder or qualified technician to confirm the plug specification for a modified setup.
How we selected these options
We prioritized traceable manufacturer part numbers, documented application examples and clear distinctions between OE-style and aftermarket designs. We checked Mopar and NGK sources on October 4, 2026 and separately verified the identity of the linked Amazon eight-pack. Historical catalogs and manuals are labeled by year; they do not establish current stock or replace a current vehicle lookup. We did not buy, install, dyno-test or assign numerical performance scores to these plugs.
Image note: The featured image is an AI-generated editorial illustration, not a photograph of a reviewed product.
