The other day I was chatting with the dealer about doing the scheduled maint. myself and keeping the factory warranty happy. I asked him why you need to change the plugs every 30000 miles when most new vehicles nowadays go 100000 between changes. He mentioned that you need to use regular copper plugs in the Hemi, not platinums, hence the reason. I then mentioned that I recently changed the plugs and installed Autolite Plat. XP's and asked if I should be concerned. I was told that the reasoning behind using standard plugs is thatfor some reason platinum plugs have a hard time firing correctly in the Hemi. So what will probably happen is that the truck will run fine for a while then you will start getting misfire codes due to the plugs fouling with the incomplete combustion. The gas mileage will also suffer (I have noticed this, but I figured it was due to going up a size in tire and not recalibrating the speedometer; I guess not). So for now I still have the plugs in and will probably keep them in until they start to give me problems, or I get really ambitious one afternoon and decide to go ahead and change them (soooo much fun). Just wanted to give you fellow Hemi owners a heads up and I was wondering if anyone else had heard about this.

 

Aw damn... Every 30 grand??? I'm at 34,500.... Hmm guess i should change em...

 

I think that dealer was feeding you a line of bolognie. There are many who have put platinum plugs and iridium plugs in their Hemis, with no ill effect.

The reason the standard plugs are rated for 30k, is because they are copper and each plug fires twice during each stroke; once on compression and once on exhaust. On a conventional V8, each plug fires only once on compression.

I've been running NGK platinum plugs for several years in my '04 with no issues whatsoever.

 

No, that is true, one of my buddys is a tech at the dealer. He has to get certified every year and the hemis were not designed to run on platinum, if they were they would of put them in there.

 

I'm no expert on engines, but I don't see how you can design an engine to run on a certain type of spark plug...

 

well I can see why someone would design an engine that would use the spark plugs that wear out every 30k, That way they get you with the service of them spark plugs every 30k miles its good for there service department as you know they don't change them cheap spark plugs for cheap in these hemis.

 

I put Champion 3570 (Platinum plug) in my Hemi and they started to misfire like mad. I had trouble starting the truck and it would sputter at idle and shut off. The plugs had fouled out in 8 months (12k miles) after installion. (And Championdon't stand behind there plugs. They claimed itwas the trucks fault that the plugs were fouled.SoNO refund for sh*ty plugs) Now I have the NGK 5306 (Copper plug) and no problems so far.

 

In talking with the local Dodge Service Department, the technician told me that the standardOEM el-cheapos are lasting quite a while, and he hasn't seen the need to change them before 50k to 60k miles.The manual says to change either at 30kor 60k miles depending on severe or light duty maintenance schedule.

I plan on changing mine at 45k miles.

BTW, each plug doesn't actually fire twice per cycle. Here is my understanding of how it works:

There are two plugs for each cylinder head, and there are 8 ignition coils that each fire two plugs (for a total of 16 plugs). When a coil is fired, one plug fires for at the start of acombustion cycle ona givencylinder, while another fires in the middle of a previous combustion cycle on a different cylinder to completely ignite the fuel/air mixture and create a more complete flame front and combustion cycle.

 

I've had NGK Iridiums for over 10,000 miles without a stutter/missfire or decreasing milleage figures.
I also run either petrol or LPG in my Hemi.
No problems so far...................... fingers crossed.
Al.

 

Over the years and many cars from POS's to High Performance from Imports to Domestic, I have always had the best luck with a set of clean, copper core plugs. I've tried a lot of the fancy plugs but always wind up going back to simple. The only other plugs I've tried and liked are the Bosch +4's and their truck plug. These seem to hold up pretty well in myJeeps but for the cost difference and negligible performance, copper cores usually go in them now.

And I will continue to hate AC Delco plugs! I lost a very expensive balanced and blueprintedracing engine in one of my Camaro's because the electrode broke off the end and welded itself to the cylinder wall at 90mph.

just my 2 pennies.