Am I going to damage my engine with Platinum Spark Plugs?

I have a 1999 Jeep Grand Cherokee with a 4L inline 6 cyl engine. So much research indicates that plain old copper plugs, Champion resistor plugs are the OEM, work best in my engine. Unfortunately, I got talked into an “upgrade” to platinum at the car parts store. I installed the Champion single platinums that are recommended by Champion for my engine (3034, RC12PEC5). They are supposedly the same heat range as the OEM plugs and have the same resistance.

There is much scary opinion to be found on various Jeep sites about using Platinums.

SO, my question is, am I going to HARM my engine with these things? My impression is that the car runs better, but I don’t want to risk damage to the engine. And, having spent the money I’d prefer not to have to replace them with copper if they aren’t going to do any harm.

Anyone know if I am OK leaving things as they are for the next 30K miles?

The plugs for that engine have the electrodes lengthened more than any other OE plug and the ceramic insulators are fragile. If that electrode breaks off it could cause a great deal of damage. Platinum plugs have a reputation for having weak center electrodes and even the most common, short electrode plugs seem prone to breaking. Replacing plugs with the original brand and part number is usually the best option on all engines especially that one.

Nothing wrong with platinum. What you gain is time/mileage between tune ups, yet you pay more for them. Over the life of the truck, when do you spend less money ? Buying cheaper copper plugs more often ? Buying costlier platinums less often ?

The true key to dammage or not is in the physical dimensions of the plug and if the parts store says they interchange then you won’t have a problem there.

The engine in your Jeep began it’s long career powering Ramblers in the late 1950’s…It does not care what kind of spark plugs you put in it as long as they spark. About the only way you can damage this engine would be to run it without any oil or pour sand in it…

The platinum plugs were an “upsell” This is America, what else is new??

If you find these plugs listed by Champion as OK for your engine, I wouldn’t worry about using them, but I don’t know about Jeeps in particular. I do doubt it runs any different that it would with fresh regular plugs. Just curious, what ‘scary opinions’ are out there? Anything backed up by actual facts?

I found a post at stating that:
To prevent possible pre-ignition and/or mechanical engine damage, the correct type/heat range/number spark plug must be used.

CAUTION: The standard 4.7L engine uses copper core ground electrode spark plugs, they must be replaced with the same type/number spark plug as the original. If another spark plug is substituted, pre-ignition will result.

An then it goes on to state similarly dire consequences from using copper plugs in the engines that OEMs Platinum.

I haven’t opened the hood of a car in a decade, since everything became electronic. I just figured engines became as fragile as computers. WhadduIknow!


This is pure B.S. This engine, with its 9 to 1 compression and open combustion chamber is virtually immune to pre-ignition. You could not make it knock if you wanted to…I don’t know how people come up with this stuff…

The plugs will be fine and perfectly safe. All factors including dimensional parameters have been considered when specifying that plug for your vehicle.

The only difference in copper plugs, platinum plugs, and irridium plugs is the electrode material. Platinum erodes less quickly and irridium less quickly still.

I personally have never heard of a problem with electrode breakage except in cases where people have tried to adjust irridium electrodes. They’re too brittle to be bent.

As long as the plugs are identical in length and heat range there should be no problem.
The reason for platinums is that the Federal emissions warranty (unless it’s changed) required that spark plugs be warranted for 24k miles.

Platinums, on average, last longer than copper core plugs and the odds of a platinum plug developing a misfire during the first 24k miles is less than a copper core.
As to anything else (economy, performance, etc.) it’s a wash.

I always wondered about this, wouldn’t the manufactures warranty cover plugs out to at least 24K?. The shortest warranty I remember was 3 years 36,000 for mid-90’s GM’s.

Are they saying that if your plugs fail at 24K (on a 3/36 car) and you have 4 years on the car,your covered? I don’t think so, the Fed warranty is 2yrs 24K,shorter than the standard manufacture warranty.

Spark plugs are a “normal replacement item” like clutches, wiper blades and brake shoes and are NEVER covered under warranty…

As far as I know, the emissions warranty covers plugs for 2 years/24k miles. While I did not cut and paste the entire bureaucratic mumbo-jumbo, here’s a few EPA excerpts.

What Emission Control and Emission Related Parts Are Covered by The Design and Defect Warranty?
An emission control part is any part installed with the primary purpose of controlling emissions. An emission related part is any part that has an effect on emissions. Listed below are some examples of parts or systems which fall under these definitions. A more complete list can be found in your owner’s manual/warranty booklet. If any of the parts listed below fail to function or function improperly because of a defect in materials or workmanship, causing your vehicle to exceed federal emission standards, they should be repaired or replaced under the emissions warranty if your vehicle is less than 2 years old and has been driven less than 24,000 miles. One manufacturer may use more parts than another, so the following list is not complete for all vehicles.

Skipping the normal emissions warranted stuff led to this.

These are examples of other parts of your vehicle which have a primary purpose other than emissions control but which nevertheless have significant effects on your vehicle’s emissions. If any of these parts fail to function or function improperly, your vehicle’s emissions may exceed federal standards. Therefore, when any of the parts of the following systems are defective in materials or workmanship and have failed in a way that would be likely to cause your vehicle’s emissions to exceed federal standards, they should be repaired or replaced under the emissions warranty:

1.Fuel Injection System: fuel distributor
2.Air Induction System: turbocharger, intake manifold
3.Exhaust System: exhaust manifold
4.Ignition System: distributor, spark plugs, ignition wires and coil
5.Miscellaneous Parts: hoses, gaskets, brackets, clamps, and other accessories used in the above systems.

Although it grated on me to no end I had to wrestle several barbecued Subaru turbochargers that were replaced under an emissions warranty and the cause of failure was coked engine oil due to not changing the oil on a regular enough basis and thrashing the car.

My opinion re platinum and irridium plugs is from personal observations. Anyone curious about the problem could buy a few spark plugs and compare the amount of pressure needed to break the plugs electrodes on various part numbers. Particular attention might be paid to the length of the Jeep 4.0L’s electrodes.

I would be really amazed to here that a Platinum plug is harmful. If there was any sort of problem like this you’d hear about it EVERYWHERE. There must be well OVER 100 billion miles driven world-wide on Platinum or Iridium plugs over the past 20+ years. My wife and daughter and I have driven well over a combined mileage of 500k miles without one incident.

Not wishing to sound alarmist, however, I have seen the results of dropped center electrodes on more than one occasion. If my memory serves me, it was, in fact, on the original car talk forum 15+ years ago that I noted the second or possibly third engine failure due to dropped electrodes on platinum plugs and was chastised by a fellow poster who was an employee of the spark plug manufacturer in question. I have seen several more since then.

BTW, the original forum’s Rant & Rave was an outstanding source for entertaining and enlightening intercourse. It was a shame it couldn’t survive the evolution of the web.

You have to be really careful when adjusting the gap on these super tiny iridium plugs. Any pressure applied to the center electrode when adjusting the ground electrode tang for gap can snap off the center electrode. An iridium pellet is welded onto the base electrode material. I bought a few of the more expensive NGK Iridium IX-Treme to harvest the electrodes for a project at work. No wonder they’re insanely expensive, welding that tiny center electrode must be a costly operation compared to the traditional spark plug construction.

Use the platinum plug. I’m sure if you look hard enough you’ll find an article about how someone poked their eye out with copper core plug, so they must be dangerous as well? Platinum are less prone to fouling as the center electrode has less area for build up to take place, and each firing will burn it off if carbon was to try and build up. They usually come pre gapped, so you can simply pop them in. In many years of working on cars, I’ve never heard of the center electrode falling off on platinum plug. I’m sure it happens, but I don’t think it is a systemic problem.

That’s a post about the 4.7l v8, right? Not your 4l I6. Regardless, you should be fine.

One or two are a minuscule amount. There are MILLIONS of Platinum plugs running THOUSANDS of miles every year. In order for there to be “Problem” we’d be seeing THOUSANDS of plugs failings. Based on the questions in this forum I don’t see too many Platinum plug failures either.

SO, just to extend the paranoia…

I never thought of plugs as particularly fragile if you didn’t do something stupid like try to lever the adjusting tool against the porcelan to adjust the tang. But, the two cautions that I hear are:

  1. Don’t use a wire gage to gap Platinum plugs because you may weaken the bit of Platinum welded to the copper core, causing it to fail in some catastrophic way. Of course I used a wire gage.

  2. And from this forum, “I personally have never heard of a problem with electrode breakage except in cases where people have tried to adjust irridium electrodes. They’re too brittle to be bent.”

Is the electrode “tang” also Platinum? I would assume that the tang that you bend to gap a plug is the same soft metal as on a regular plug. If not, I’m screwed because all of my plugs that were supposed to come pre-gapped needed significant adjusting to get them close to the correct gap.