This engine is engine stays on the production line for almost 20 years now. It’s not without a reason: while having the outdated OHV configuration, it shows great levels of performance and efficiency. A big part of it is that it has two spark plugs per cylinder. Two sparks ignite the air-fuel mixture more evenly generating more force for the power stroke.
Since spark plugs are such an important thing for this engine, we’ll dive deep into the topic. In this article, we’ll see how to choose the right spark plugs for the 5.7 HEMI engine so as products that can be called “best”.
Table of Contents
Factory 5.7 HEMI Spark Plug Specifications
The best way to find proper specifications is to look at OEM spark plugs for the 5.7 HEMI engine in Dodge’s owner’s manual. It recommends Champion RE14MCC4 for 2003-2008 engines and NGK LZFR5C-11 for 2009+ engines – we’ll be using it as a reference to validate the perfect fit for other spark plugs.
Pre-Eagle 5.7 HEMI (2003-2009)
|Thread size||14 mm x 1.25 mm|
|Heat range||14 (NGK’s 5)|
|Gap||.039″ (1.0 mm)|
Eagle 5.7 HEMI (2009-present)
|Thread size||14 mm x 1.25 mm|
|Gap||.043″ (1.1 mm)|
Best Spark Plugs for 2003-2008 5.7 HEMI (Pre-Eagle)
1. Bosch HR9SII330X - Best Spark Plugs for 5.7 HEMI (pre-Eagle)
Bosh is a synonym for reliability. The manufacturer states they can run up to 100k miles, but in practice, double iridium plugs can last up to 120k miles with no problem. Also, it features a unique welding technique, increasing its reliability even further.
It features modern electrode designs: fine wire for the center electrode and taper cut for the ground. This combination requires less voltage for a spark to occur and improves combustion. Also, thanks to reliable materials and manufacturing technology, it saves your engine from misfiring, providing smooth acceleration and idling.
Also, it features an increased gap from .039″ to .043″ (Eagle-like), which creates a bigger spark for better ignition.
Double iridium spark plug with effective electrodes design with a price under 7 dollars per piece – absolutely the best deal on a market. For a reference: OE nickel NGK LZFR5C-11 costs $6, but runs 4(!) times less.
- Incredible reliability and lifespan
- Increases engine’s performance and efficiency
- Outstanding value for a price
2. Autolite XP5263 – Good Alternative
Iridium-platinum center electrode combined with platinum ground electrode provide an amazing lifespan increase, compared to OE plugs – they run up to 100k miles. Yet, they lose to our #1 in this regard: iridium-platinum is slightly worse than double iridium.
They are very similar to Bosch plugs, featuring fine wire + taper cut electrodes, providing great combustion efficiency. The only flow is a gap: it has OE .039″ gap, but we know that it was revised to .043″, thus .039″ is too small for the HEMI.
They cost the same as our #1, but slightly loose in terms of reliability and performance. But it’s not a bad spark plug for HEMI by any means, it’s nevertheless way better than OE copper plugs.
- Good lifespan
- Good performance
- Good value
- Slightly worse performance and reliability compared to Bosch HR9SII330X
3. Champion RE14PMC – The Cheapest, OEM Analog
Compared to OE Champion 570, the ground electrode is coated with platinum, which adds extra 10k miles to the lifespan according to the manufacturers. But there are many cases when copper Champions were running well over their factory mileage, so you can expect a real lifespan of 3570’s around 50k miles.
Efficiency is where the majority of changes happened. Ground electrode, besides improved materials, got rid of corners that were obstructing fire from spreading. The center electrode becomes cone-shaped, reducing the load on an electric system, therefore decreasing misfires. Last but not least, the gap was increased to .045″ – it’s the biggest gap out there, which positively impacts performance.
Those plugs last for twice less than the previous. Instead, they cost 40% less and provide top-level performance. If you don’t want to spend over $100 for a set of 16 plugs, those are for you.
- OEM analog
- Great performance
Best Spark Plugs for 2009+ 5.7 HEMI (Eagle)
1. Autolite XP5325 – Best Spark Plugs for 5.7 HEMI 2009+
This Autolite model has iridium-platinum center electrode with platinum ground electrode. This combo ensures lifespan up to 100k miles – more than 3x of copper ones.
It has the best-in-class performance for 3 reasons:
- Taper-cut ground electrode design: cut and rounded angles improve the fire spread.
- Increased gap: spark is longer by .002″, meaning it can ignite more A/F mixture.
- Reliable materials exclude any misfires for a long time.
Those plugs provide great lifespan and performance for extra $2 dollars from OE NGKs – superb deal! They live ~17% shorter compared to Bosch, but they cost 30% less, making them most cost-effective spark plugs for 5.7 HEMI.
- Great performance
- Good reliability
- Good value
2. Bosch FR8SII33X - Best Reliability
Bosch states it can run for 100k miles – the same as others we’ve seen earlier. But in reality, they have both electrodes with iridium discs, which is significantly better than the platinum-iridium pair resulting range increase up to 120k miles.
With taper cut ground electrode and fine wire center electrode, air-fuel mixture spreads considerably faster, thus improving efficiency and performance. Also, it features increased gap from revised OE plugs, which positively impacts performance.
They provide outstanding performance and reliability, but with a higher price, making them #2. Considering HEMI has 16 spark plugs, replacing the thole set may be costly, but Bosch 100% worth it price.
- Superb reliability
- Good performance
3. NGK LZFR5CI-11 – OE Replacement for a 5.7 HEMI
You can tell it from the name: it’s an iridium analog of OE NGK LZFR5C-11. New materials improve the lifespan to 100k miles.
Materials improved, but electrode design stayed the same, so the performance is on the same level – descent, not more.
With the price of $7-$8 dollars it provides good value for the price: paying ~$120 for the set and driving for 100k miles sound sweet. Yet they have outdated electrode design, which keeps it away from the top-2.
- OEM analog
Spark Plugs Characteristics Reference
First of all, we need to make sure our new spark plugs will fit the factory seats. There are 3 parameters responsible for the right fitment.
- Thread Diameter
For 5.7 HEMI, thread diameter is 14 mm.
- Thread Pitch
The thread pitch must be 1.25 mm to fit the engine
The reach should be neither more or less than 25 mm.
All plugs we’ve selected have the correct fitment parameters, so we won’t mention them in reviews.
The manufacturer recommends using nickel spark plugs, but it’s better to use platinum or iridium spark plugs because they have a much better lifespan and can be used instead of nickel in any engine. Considering it, the best plugs for 5.7 HEMI have to be made of iridium or platinum, while having other characteristics the same as OEM plugs.
The recommended gap for 5.7 HEMI is 0.039-0.043 inches or 1.0-1.1 mm. If you’re thinking of gapping to get a bigger spark for improved performance and fuel efficiency, forget it. Since HEMI has 2 spark plugs per cylinder, you are having twice bigger the spark as other engines, so there is no point in the gap increasing while risking to get misfires. Also remember: you cannot gap platinum or iridium plugs, because you can damage the reinforced covering.
Heat rangeThe heat range of recommended spark plugs is 5, and the NGK’s heat range varies from 2 to 11 (2 is the hottest, 11 is the coldest). Note that heat range is not unified across all spark plugs manufacturers. Knowing that we are looking for a heat range that will be equal to NGK’s 5.
Best spark plug wires for 5.7 HEMISpark plugs aren’t the only thing responsible for the spark occurring. Before plugs, high voltage travels through wires – if their conductivity is bad, electric current drops, leading to misfires.
When to change spark plug wires?Spark plug wires wares too, so they need to be changed at least every 100k miles. But it’s always a good idea to check them with shorter intervals.
APDTY Spark Plugs & Wires Kit – All-in-oneThis set includes 16 OE Champion 570 copper spark plugs and 16 wires with plug boots – only for $120. It’s the price for a set of 16 platinum or iridium plugs without wires – a great deal if it’s time to change both wires and plugs. OE copper plugs run good but not too long – 30k miles only. But you can upgrade them when their time comes and still be having relatively fresh wires.
Standard Motor 7884K – Cheap OEM Replacement
If you need just wires, go for them. OEM wires are hard to get and they are pricey. Those have 7 mm width, but it should be fine for OE-gapped plugs, especially for those with fine-wire or conned center electrode.
MSD 32039 – Performance wiresThose are short and beefy wires that have super low resistance, providing outstanding conductivity. Compared to OEM 8 mm wires, those are 10.5 mm – may not seem too big of a difference, but wire area increased 60% (50 mm² vs 86 mm²). If you have gapped plugs, those are a perfect match since an increased gap requires more electric current, which is determined by conductivity and voltage.
Advice How to Save Money: Change Spark Plugs by Yourself
This process is easier than you may think and don’t require much skill or fancy tools. All you’ll need is a swivel spark plug 5/8″ (16 mm) socket and half of an hour of free time. This way you are saving $100-$200 in labor that you can spend on better plugs.
- 5.7 HEMI have been revised in 2009, so there are 2 versions of the engine with different spark plugs: pre-Eagle (2003-2008) and Eagle (2009-present)
- OEM spark plugs for 5.7 HEMI pre-Eagle are Champion 570 RE14MCC4
- Best spark plugs for 5.7 HEMI 2003-2008 are Bosch HR9SII330X.
- OEM spark plugs for 5.7 HEMI Eagle are NGK LZFR5C-11.
- Best spark plugs for 5.7 HEMI 2009+ are Autolite XP5325.
- Iridium is the best material for 5.7 HEMI spark plugs.
- Both OE copper plugs are outdated and not the best options for 5.7 HEMI of any year.
- Don’t forget to check the wires.
- Consider DIY spark plug change.
How many spark plugs does a 5.7 HEMI engine have?
5.7 HEMI has 2 spark plugs per cylinder with a total of 16 for an entire engine for both first (2003-2009) and second (2009-present) versions.
How to check if I need to change the spark plugs?
The most common signs: misfires, increased fuel consumption, the car is jerking while accelerating, trouble starting, and rough idling.
How often should I change spark plugs in 5.7 HEMI?
The longevity of a spark plug depends on its materials: change copper/nickel every 30k miles, platinum – 60k, double platinum – 80k, iridium – 100k.
What spark plug heat range is optimal for 5.7 HEMI?
The best heat range for 5.7 HEMI is 5 in NKG’s gradation and its equivalents from other brands. Since all spark plug manufacturers have their own ranges: NGK – 5; Champion – 11,12; Bosch – 8; Denso - 16; Autolite – 37. E3 ACDelco cannot be referenced.
What gap is optimal for 5.7 HEMI spark plugs?
The recommended spark gap for 5.7 HEMI is .043 inches or 1.1 millimeters.
What are the best spark plugs for 5.7 HEMI?
For pre-Eagle engines (2003-2008) it’s Bosch HR9SII330X, for Eagle HEMI (2009-present) it’s Autolite XP5325.
What spark plugs are recommended for 5.7 HEMI?
From the Dodge owner’s manual, the recommended spark plugs for 2003-2008 HEMI are Champion RE14MCC4, and for 2009+ HEMI are NGK LZFR5C-11, but it’s better to upgrade to platinum or iridium spark plugs.