Copper versus Platinum, Iridium, all the other iums . .

This spring I plan on changing out the spark plugs for my 04 Dakota 3.7L. My grandfather was the previous owner and I can’t ask him what he put in there, he passed away, and I couldn’t find any records he kept to show what type is in there.

I have read that many recommend putting in the copper tip plugs into that specific engine. I have never used copper tip plugs before and my good ol repair guide for the Dakota/Durango doesn’t recommend anything.

Anyone have any experience they wish to share or what you would recommend?


Look in the manual, or find one online.

Go with whatever is listed in there. Don’t try to “upgrade” or “enhance” or spend more money for “hotter” plugs. It will do you no good, unless your goal is to empty your wallet.

Trying to use something other than what the manual specifies opens the door to weird problems later. OEM is the safest route.


The online Dodge owners manual says:

“Check the Vehicle Emissions
Control Information label for the proper type of spark
plug for your vehicle”

So that information is sitting in your engine compartment.


Mopar says this for the '04 3.7L: 2002-2012 Mopar Spark Plug SPZFR6F11G | MOPAR Parts On Sale

It’s always best to use exact OEM replacement.

1 Like

You can use aftermarket plugs as long as they meet the specifications of the OEM plug. You can even upgrade to a newer platinum or iridium plug that meets the OEM specs. The important thing is that all the plugs are the same.

The updated plugs may have a different impedance that they present to the coil, and therefore fire at a different voltage. If the voltage difference between the plugs is very high, then the computer will see that as a misfire.

You need to decide whether the upgraded plugs are worth it. Iridium plugs can last up to 4x longer than copper plugs, double platinum 3x longer. That can be important if the plugs are very difficult to replace. Not so important if there isn’t much service life left in the vehicle.

1 Like

Sorry for your loss. I have no experience w/that particular vehicle/engine , but the disadvantage of copper plugs is they must be replaced sooner; the advantage of copper is exactly the same, that they must be replaced sooner. Sooner replacement is better imo b/c less chance they’ll get stuck after being installed for many, many hours of use. Copper plugs are the practical compromise, as long as they are consistent w/the specs in the owner’s manual/emissions sticker.

Another factor: W/some engine configurations, replacing the plugs is a time consuming chore, so take that into account as well . I’m seeing a little over an hour to replace. ZFR6F-11G (NGK) is the recommended plug from what I can tell. I think that’s a copper v-power, same type I use in my Corolla. The “V” seems to help with the emissions. However, always go by the owners manual or emission sticker when selecting parts for your Dakota.

1 Like

Could always pull one and look at it to see what he put in it last time… Just saying…

Sorry for your loss…

I’m sure your grandfather would be pleased to know you’re taking excellent care of his truck :smiley:


True, I am just waiting to take them all out and I am the type that would take one out and go, well guess I’ll take them all out lol

Appreciate the link, OEM is what I try my best to stick with.

I do my best, he was very good to it and it def means alot to me.

Yeah this will be the first time I do a V6 changing out the plugs, but with this one just the air box has to come off and some of the hoses just moved so not too bad. This is the first time anyone has recommended checking the emissions label so I def learned something new. Appreciate the info!

It appears the factory Mopar (SPZFR6F11G) plug for your car has a nickel alloy tip, instead of platinum or iridium.

Platinum and iridium tip plugs are for LONGEVITY. NOT performance. If they were then every NASCAR driver would be using them - They don’t. Copper and nickel alloy tip give the best performance for your vehicle. I always stich with OEM manufacturer - either directly from dealer or from independent. example - My toyota highlander sparkplugs are made for toyota by either Denso or NGK. I’ll buy either of them instead of from Toyota.


Do older cars (2003) w/FI and copper plugs benefit from high tech plugs?

My 2005 V6 4Runner specifies copper and my mechanic says to stick with the original recommendation.

Not that ive found.

1 Like

I use to own an 05 4runner V6. From the factory - Drivers side were Denso, and passenger side were NGK. I replaced all 6 with NGK.

Completely agree. On an older car, especially with a carb, “cokeing”
was much more of a problem than wear on the plug so replacement was much more frequent.

As a general guide, manufacturers replacements are always good but if you want to switch to a more modern plug it won’t hurt but it also won’t make any improvement. OTOH if you want to avoid a major PITA from galling plugs I would strongly suggest following the manufacturer’s replacement interval. It may be a 100,000 mile plug but if your vehicle is designed for 30,000 mile replacement you might have a very unpleasant experience trying to remove it .