Skrimps

Hello everyone,

Havent spent many hours reading about spark plugs for the 4.6 2v. I purchased an 02 GT a few weeks ago. The previous owner put Autolite Iridium plugs in the car. Seems to run fine, but are these plugs good to go? I have read a lot of posts about running copper plugs, or motorcraft plugs only....or going down 1 step on the heat range. I get that the advantage of Iridium plugs are longevity, but is this plug really necessary for my car or should I consider Motorcraft platinum plugs or coppers like Autolite or NGK?

ZEN357

Go with E3 Diamond Fire Spark Plugs. You can get them form Jegs or Summit Racing. You'll be glad you did.

Derf00

Unless you have a special application like Forced Induction or a race-ready motor etc, a plug is a plug. You can use Motorcraft, Autolite, or NGK. Aside from longevity, there's not a lot of difference between standard, platinum, or iridium except a lighter wallet with each step up. Pick up some Motorcraft or Autolite platinum plugs and be done. The best compromise in price and longevity.

WJL

Can't say it any better than Derf00, if you search this forum for posts by Cliffyk you will find everything you need to know about spark plugs

Skrimps

Thanks for the advice. It came with Autolite Iridiums that the previous owner just installed before I bought the car. Just wasn't sure if it was recommended to run iridiums in this engine over the Motorcraft platinums but sounds like it really doesn't matter. I think I will double check torque on them and run em for a bit.

08'MustangDude

By far COPPER PLUGS are the best, but they don't last more than 30,000 miles,
when they start to hinder performance as they wear and the GAP widens. They are
best for performance, while being the worst in longevity.

If you don't put a ton of miles on, you can use copper. If you're only gonna put 10,000
miles a year on the car, copper is fine, you'd be changing them every three years.

Diamond fire is a hoax, they are no better than your average platinum plug.
You need more spark energy for Platinum, and Iridium, they are not better
conductors than copper. Due to their slight resistance as a result, platinum
and iridium plugs actually generate their own heat.

You can't use gold or silver, which both conduct better than copper, but they'd
melt almost instantly.

When I replace the plugs on my 2008, if they have copper, I am going to use them.
Top performance and MPG from copper. I won't be running the '08, maybe once a
week I do, so it will be fine.

WJL

Here's a quote from Cliffyk, better than a google search

"^+1, all gimmick plugs are a waste of money--think about it:

If there were some better way to make spark plugs Champion would have at some place in their 105+ years come across it;

If there were someway to make spark plugs that instantly provided more power and fuel economy then the manufactures would install them at the factory. More power and fuel economy would provide something for the marketing department, and improved fuel economy would help them better meet the CAFE standards and reduce the fines they pay for not meeting the standards.

The they (the manufacturers) don't, because they (the spark plugs) don't..."
__________________
-cliff knight-

97autumorangeGTS

^^^^^^^^^^^^^^ 110%

08'MustangDude

Not entirely true. I have seen them remove items to save money, like removing windshield trim
side pieces (outside), when a previous year model had the trim. Even if a line item being removed
saves $1.00, times that by the # of cars they made. Iridium spark plugs are expensive, they can
be $8.00+ a piece. If the factory can use Platinum at $5.00 each to get the same performance, they
will use them and save the $3.00 times # of cylinders, times the # of cars...

Then, on the other hand, I have seen them ADD line items when it gets close to year end. My 2013
Jetta TDI w/Premium did not have plastic covers on the trunk lid arms, yet the other person, who bought
theirs later in the year, DID.

That's like saying if CAIs got you better performance and MPG, they'd put them on at the factory, and
they don't. Though, most are already CAIs (pull air from outside the engine compartment), they
don't put the nice looking ones on. Why don't they use K&N or other ho-flow air filters at the factory?
COST, not for better anything. Most of the time, if the manufacturer does not make a CAI for the car,
it won't do much good buying one elsewhere to use on a stock motor. I know Mopar makes their
own CAIs, and you can order their car with one, if available. Roush makes them for the Mustang,
and you can order those upgrades from factory, not just after you buy the car.

As far as spark plugs go, they install the ones that will perform the best for the cost. They will
not install a iridium where a platinum one will do. Plus, if you're not turbo/super charged, you don't need
iridium. If you don't have VVT, you don't need iridium. In most cases you don't even need the
fine tip platinum, unless you're boosted or VVT. For a 4.0 mustang, for example, you can use just about
any cheap platinum plug. The reason my TSI has iridium is because of the boost and timing advance
changes the ECU does under boost. These plugs have to be fine tip, and gaped at .028 - .032, 0.28
when at +6 boost. If I were to use BETTER copper plugs, it would be all messed up, and sloppy...
Copper plugs are the BEST, and they can't use them with these new VVT motors, so they have to
up the spark energy to compensate using platinum or iridium plugs.

They let US pay for the better performance, they aren't going to do it unless there is a package for it.

Even this guys motor, if he's a 10,000 miles a year or less driver, copper plugs will be just fine.

I had a 2006 Jeep liberty, and it came from the factory with copper plugs. If you used anything
other than copper? You're 17MPG City went down to 15, unless you got higher energy coil on plug
packs for a platinum plug to make up for the spark energy loss.

This is how I see it, and have seen it...

WJL

"CAFE levels that manufacturers' fleets are required to meet in that model year, specific levels depending on the characteristics and mix of vehicles produced by each manufacturer. If the average fuel economy of a manufacturer's annual fleet of vehicle production falls below the applicable requirement, the manufacturer must either apply sufficient CAFE credits to cover the shortfall or pay a penalty, currently $5.50 per 0.1 mpg under the standard, multiplied by the manufacturer's total production for the U.S. domestic market."

Quote is from Wikipedia.

Using your own theory, E3's would be a bargain for them.

I think how they calculate it has recently changed, known as vehicle footprint method