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Discussion Starter · #1 ·
Seeing the what is the best spark plug for a 3.6 makes me wonder if they are truly an improvement over Iridium?
 

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I like them. Put them in my daughter's Acura (2.4L I-4) and they seemed to pep up the motor. The platinum plugs I pulled out looked okay. I was happy enough with them that I put them in my '16 R/T 5.7 at 50k miles. Didn't notice a difference, but they'll last a long time (supposed to be longer than platinum) so all's good.
 

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For my 5.7, I installed the 96355 {#LFR5AHX} which set me back $8.38 each at RockAuto.com

The 94705 are a little pricier, but you can still get them for $8.82 at CarID
 

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Seeing the what is the best spark plug for a 3.6 makes me wonder if they are truly an improvement over Iridium?
My recommendation is use the plugs the factory calls for. You know these work and last a long time and a long time based on real world testing by Dodge.

With other plugs there is the risk they won't work as well -- in a few cases I've come across over the years the new replacement plugs made the engine run poorly -- or they won't last as long.

If you change factory plugs at X miles and the engine runs better that is a sign the plugs were run too long. I have no Dodge experience but with other cars and a number of times over the years I had the plugs changed at the miles called for by the factory and not once did new plugs make any noticeable difference. This told me the plugs were not yet to the point they were (obviously) affecting engine performance. But I have no problem changing the plugs "early". I'd rather leave a few K miles on the old plugs than run them too long and possibly load up the engine with deposits from poor combustion or worse have a plug suffer a mechanical failure and drop a ground electrode into the cylinder or have the ceramic tip fracture and drop this material into the cylinder.
 

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Discussion Starter · #6 ·
It's not just more miles out of the plugs. It seems they supposedly use less voltage to fire.
 

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Discussion Starter · #7 ·
I can get Autolite Iridium much cheaper than the NGK. I used to really like Autolite, much like AC Delco, since moving to China, not quite as nice as a few years back. I see they just redid the lines of spark plugs. Not sure which way to go.
 

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It's not just more miles out of the plugs. It seems they supposedly use less voltage to fire.
There is no benefit in this regard. The coils still still generate the same high voltage regardless of the plugs used.

If the plugs truly need less voltage my concern would be this can result in subjecting them to too high a voltage which can result in a shorter service life.
 

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Spark plugs fire at the lowest possible voltage depending upon condition of the plug and gap distance. You can prove this with a conventional coil and a high-voltage ignition tester. A gap of only .020" will fire at 9K volts. Open the gap to .060" and the voltage will be about 22K volts. Electricity is lazy. It fires at the least possible voltage. When the primary field of the coil collapses, it induces a high voltage in the secondary. During the rise time, the spark will jump the gap at the LOWEST possible voltage depending on conditions stated. Another thing. If both electrodes are sharpened to a pinpoint, the plug will fire at an even lower voltage.
-John
 

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Discussion Starter · #10 ·
I think the Autolite are worth a try, $4 and change per plug.
 

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Anybody remember AC Fire Ring spark plugs? The center electrode was a spline. More sharp points to fire from. They went away in 1975 with the advent of the GM HEI distributors. Lots of GM based hot rodders still swear by them due to their stone cold reliability. Different versions of the AC spark plug also fired the 2nd & 3rd stage of the Saturn V rocket that took us to the moon. Delco also made critical components for the lunar rover including spark plugs for many commercial jet engines today.
Before dynamometers were everywhere, Drag Racers during the period between the 1950's and early 1970's always got better power using the fire ring plug because they fired with lower secondary voltage. This was critical during the Kettering Ignition (points/condenser) era.
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-John
 

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Discussion Starter · #12 ·
Spark plugs fire at the lowest possible voltage depending upon condition of the plug and gap distance. You can prove this with a conventional coil and a high-voltage ignition tester. A gap of only .020" will fire at 9K volts. Open the gap to .060" and the voltage will be about 22K volts. Electricity is lazy. It fires at the least possible voltage. When the primary field of the coil collapses, it induces a high voltage in the secondary. During the rise time, the spark will jump the gap at the LOWEST possible voltage depending on conditions stated. Another thing. If both electrodes are sharpened to a pinpoint, the plug will fire at an even lower voltage.
-John
Being an Oldsmobile guy, I have dealt with the .080" factory gap, it wore a bit and it doesn't start. Oldsmobile actually had a TSB to change it to .060". I run them at a loose .045".
 
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