Spark plug recommendations. | Ford Explorer Forums - Serious Explorations

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Spark plug recommendations.


New Member
April 14, 2011
Reaction score
City, State
Melbourne, Victoria
Year, Model & Trim Level
2002 XLT
Hi all, new member and enjoying the threads. Can anyone tell me the best spark plugs for a 4.0 lt V6 2002 and the best way to change them. Also what sort of fuel econ should I be getting. Ltr/100km please, don't get miles and gallons.:australia:australia I've had the car for 3 years and it seems to be getting worst. Mechanic said change the plugs.

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whoa how is Melbourne, Victoria in the uk?

Melbourne Australia. Not the UK. But it's going well over here, starting to get cold with winter moving in but she'll be right.

summers approaching here and allready with had some good weather. what i mean is the post has been moved into the uk section outside your zone, he may of had too many drinks to move it here.

As we don't have many 2002 explorers here. I don't think many UK owners can help you. But I'll move your post to the stock 2002 Explorer section so that you should get some answers.

Use only original Motorcraft plugs in these, they do not seem to well with aftermarket plugs.

Be sure to inspect the plugs when you pull them for clues as to why the plugs are thought to be the culprit. I'm assuming that you have no CELs?

Most folks here will tell you that the 4.0 gets very little better mileage than the 4.6L.

My 4.6L got 15.9 mpg when we lived on the mainland, and took long trips which got the mileage up.

However, here it averages 15.4 mpg, with 95% of that being on surface roads/city streets and no long trips (obviously).

Those are in standard, not imperial gallons. :thumbsup:

Looking forward to sharing a few pints with you blokes later this summer in Sydney.

Plugs: Motorcraft. Why consider aftermarket when the factory ones last 100k miles (160000km or something haha)?

There are lots of other things to contribute to degrading fuel economy... have you recently (or ever) changed the fuel filter? Air filter?

engine was calibrated with Motorcraft plugs, no marketing gimmick either, stick with them imho.

I agree with the motorcraft.

However I would like to repeat a question I ask all the time in posts like this: RHETORICALLY asking:

If you even REMOTELY are concerned about fuel economy/costs of use, WHY would you install a part that with extended mileage (ie Platinum/Irridium/ Un-obtainium Plugs)? there is no calibration for the coil pack to know the resistence of the various plug materials, the variance is THAT small.

Especially when for 1/2 the cost you can install a good old fashioned Copper plug, maintain them @ a 15-20K interval, like in old days, & have a picture window view of what is going on inside the engine?

I get why the OE's do it: to increase the service life of the PLUG, to lock you into the more/most expensive Service interval before the 100K warranty expires! this is the ONLY benefit to special plug materials. Tested, proven, time & again. Platinum does NOTHING for performance. Irridium, nothing (actually worse over time), and all the other fancy electrode designs, materials etc all for plug life, not performance.

ANY gain found from a plug change (performance, HP-TQ or MPG) is from the plug replacement, NOT the materials or construction type.

Just tossing back out there to digest. Motorcraft copper plugs or NGK's if O'reilly is out of the FoMoCo at the time. Changed at 15K. Inspect the plugs, look for anything odd.

I will never understand the ostrich in the sand approach to vehicle maintenance. especially when the 3.0, 4.0. & SOHC 4.6 are so damn easy to change plugs on. Heck even the 4.6 DOHC in the Aviator & the Adreniline are not THAT hard...


I concur with Rob on most points. There seems to be no performance gains in $$$ plugs. Most competitive racing teams use regular plugs. Synthetic oil, YES. splitfire plugs, NO.
Auto makers utilize means to keep the comparative costs of maintenance as low as possible

Heck I wish I could find it... there was a Pit Picture of one of the E3-diamond-fire whatever team's between round thrash from 2009 or 2010 that was circulating a while ago...

the mechanic/tech was gapping AUTOLITE spark plugs!! In the pits! with people watching...

I will be first to admit I have found the limits of my beloved FoMoCo plugs in my 5.0 builds... I've actually done some spark plug testing, on a chassis dyno. Drove the car to the dyno test, 60 mile drive plugs had 3-5,000 on them. cooled the car dyno'ed the car. Cooled the car, put in fresh FoMoCo plugs, same range/same part #. Ran the dyno test... picked up 3hp 2tq at the wheels with fresh plugs. That is what everyone claims with fancy plugs. then we cooled the car again, put in identical heat range NGK, regular copper "v-power" off the shelf plugs. No other changes, laid down another 7hp & 4ft, if memory serves me. Had I reached the limits of the FoMoCo design with all of my aftermarket iginition parts & the original "balance" was no more? Good arguement.

The car was one of my Mustang II's with an EFI 306cid, TFS aluminum heads, Cobra Cam & 1.7 rockers, Cobra intake, PMS piggy-back programming, MSD billet distributor, Taylor wires, MSD coil, etc etc etc... a very typical n/a SEFI small block. 350ish to the rear wheels through a 5 speed.

The old adage "the dyno doesn't lie" may or may not hold true.

I've witnessed in person tests on '04-up S/C Cobra's changing just OE plugs for Irridium, other platinum, & even E3's.... other than the A/F going all over the place, no real change... other than the initial fresh plug jump.


ps: mechanic, thanks for having my back on a typically defensive topic.