Any preference for brand, type, metal, etc. 2002 with 3.7. I've only used NGK but engine builder says just use Champion. Curious if anyone who has used different ones in this engine has had various experiences.

NGK or Champion copper core will work.

Gyro

Use what the manufacturer recommend !

Champion are crap but it’s what most Chrysler products take, you can use big or denso if you want, I usually replace them at work with some denso long life iridium since most people don’t do spark plugs on time so it give me a little fudge room… it’s amazing how many people look at it as an oil change interval and not a service interval so they get cheap oil changes and then by the time I see it it’s a how mess… if there is more than 20k on the clock here is always more services that are due


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Denso long life HD Iridium spark plugs are super good spark plugs, they "Rock"! Cost a little more up front, but worth every penny.

I have installed them in every spark infested engine I own except my old Farmall Tractor. V8s down to chain saws!
They actually even have them for small engines like lawn mowers, chain saws, pressure washers, portable generator engines, etc...
Basically, install them and forget them for a very long time.

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I got some Champion platinum and new coil packs. This was an engine reinstall, I replaced the engine in 2015 and with ~25k miles on it had issues with misfire and turns out low compression. Engine still under warranty barely. I installed NGK plugs in 2015 and when the shop put the engine back in this year they put in NGK as well because that is all they could find. Still had the original coil packs but the injectors got cleaned and dynoed and flow checked and were good. I use NGK iridium in motorcycles (KTM, Ducati).

Don't know why engine builder would say use Champion except for that is what manufacturer recommends.

Engine having some backfiring issues and sometimes hard starting. Suspect lifter may be leaking down.

I tested the old coils today after popping off the drivers side rocker cover to check the rocker arms and lifters, primary resistance was 1.7, 1.7, 3.0, 3.5, 4, 6.4. , these may have been original with +200k miles on them. New coils and plugs and engine is much smoother running. So apparently they should be 0.6-0.9 ohm.