the different type of plug help manufactures with emmisions and any warranty issue that may involve the plugs. once the spark plugs that come on the vehicle have been removed, that warranty and emmison is voided and does not come back on the manufacture of the vehicle. replacement plugs will usually only show one part #, no reason to carry 2 different plugs when its not needed after the actual stock one have been removed.

i copied and pasted this from a tech forum:

There is a reason that there is two different plugs on your engine. This engine uses coil packs instead of a distributor. One bank fires the plugs from the plug electrode (center electrode) to the ground (side) electrode. The other bank of the engine fires the plug in reverse from the ground electrode to the center electrode. This is why there are two different plugs. If you want to change plugs go with double platiunum plugs

 

My 4.7 HO had the platiunum plugs with the small electrodes in all 8 holes, all gaped .40. They looked exactely like the one in the picture. I wondered about the white stuff on them. I put in the autolites for about 300 miles and truck started to run worse, so I put the stock ones back in. Seems to have alot more power on the stock. I'm going with the Iridiums next.

 

This is also mentioned in my father's Ford Ranger 4.0L V6 manual. However, no aftermarket company OR FORDS service department carries the second part number. It turns out that:

Ford specifies two different plug types due to cost savings. One side (bank) has a platinum tip, the other side has a platinum electrode. That makes the plug a few cents less than a plug that is completely platinum. Your owner's manual should list a single part number, (but it mentions two part numbers.) It is for the plug that is completely platinum. It is probably all you would find at a local auto parts store. You wouldn't notice a problem even if you got the plugs reversed from what it originally came with until many miles down the road when your plugs didn't last as long as they should have. Just use the recommended plug in your owner's manual and don't worry about it.

BTW, Ford does the LH/RH spark plug trick on other engines such as the 4.6L. This is only done at the factory. The service plug is platinum on both sides.




And this is a quote from a Ford forum..

"Since a DIS system uses a waste spark setup, any spark plug with dual pointed pieces of platnum will work fine. The reason for the pointed spots is that one of the spark plugs fires in the reverse direction from its pair. Another words when a coil fires, the pair of plugs attached to that coils secondary both fire. One forward and one reverse. I'll explain. From one side of the secondary to the electrode of one plug through the gap to the arm through the block to that plugs pair and arcs from the arm to the electrode and back to the other side of the secondary. This is done for each of the coils controlled by the computer and crankshaft position. Due to the reverse sparking from the arm to the electrode, a point on both arcing surfaces balances the current flow and intensity of the spark between the pairs of spark plugs. Therefore, inspect any dual platnum spark plugs for this characteristic before buying plugs. I have seen dual platnum plugs where the arm is coated with platnum not pointed. The AC Delco plugs I bought for a Chevy Cavalier have a nice point at both the arm and arm and ran approx $9.00 each, but what a difference."


For example, a Double platinum autolite plug has the platinum tips that run through, like you see on your worn plug, and a regular platinum autolite plug is simply coated.

So what it boils down too, with ford, is only half of the plugs really need to be a high quality plug, so theyput cheaper platinum plugs in the rest, ONLY from the factory, to save money in production. They are still all platinum, its just that half of them are cheaper ones. Once you get it serviced at FORD, they use only the GOOD platinum plugs.

Thats BS huh?

LoL.



BUT, I dont think ANY of this applies to our truck. If it does, Dodge doesnt really address it and just uses standard plugs. I don't think this is anything to worry about.

 

i agree cause mine is acting fine. can't say much about how long it'll last till i get there tho. I've been runnin the cheap gas with an occasional fuel cleaner anyways so i'm sure it won't help for it's half life.

 

I put the Autolites in my HO too. Fireman is right about performance suffering. At first, the idle and acceleration were smooth. Now 500 miles later, idle is back to the way it was with the platinums, acceleration is worse, and milage is down. Sorry for misleading anyone at first...I'd stick with the stockers in the HO.

 

If you pulled yours back out, did the ends look discolored more than they should have?

 

Why, if you say they work as horrible as the platinums? Might as well buy the same crappy plug results at a cheaper price.

 

You can put alot more miles on the platinums, mine has 31,000 miles. While idle is rough their is still alot more power in take off with plats than autolites. This is just my experience with them. It is interesting with the different results though. I hope Iridiums is the way to go. Thats what Im getting with one of my bonus check. (if wife doesn't spend them first)