Spark Plug questions

[Joleat]

I just replaced the plugs in my stock MKS earlier today. The car has just a tad under 50k miles. The coloration was good. Four of the six plugs were right at .040" and the other two were slightly above at around .042"-.043". I replaced them with Motorcraft SP534s gapped at .030". The car runs smooth, but I wasn't have any problems with the old plugs. I just wanted to see how they looked at around 50k miles.

 

[DJE624]

Thanks for the pics.  They don't look too bad for 50K.  With those old gaps, you should feel a little smoother running up top now.

 

[BiGMaC]

The proper plugs gapped correctly can help prevent spark blowout at higher (tuned) boost levels.  So in that case it would help performance. 

Right on!
They also prevent preignition and detonation as timing advances in a tuned ride especially.  Very important with our 11:1 compression.

 

[DRII]

I plan on getting the SP534 plugs.  should they be gapped at .28 or .30?

i also noticed that the recommended maintainence on the MKS says 'spark plugs' at 37,500 miles.  does that mean Ford recommends to replace the plugs at 37.5K?  seems kind of early for that.

also, where did you guys buy your plugs?  seems like most places are selling them about $4-$6 dollars a piece...

 

[Brucelinc]

I plan on getting the SP534 plugs.  should they be gapped at .28 or .30?

i also noticed that the recommended maintainence on the MKS says 'spark plugs' at 37,500 miles.  does that mean Ford recommends to replace the plugs at 37.5K?  seems kind of early for that.

also, where did you guys buy your plugs?  seems like most places are selling them about $4-$6 dollars a piece...

O'Reilly auto parts has them for 3.99 if you have a store locally.  I personally would not go under .030.  Mine came gapped at that.  Where are you seeing a recommendation of changing plugs at 37,500?  Is that under the severe service recommendations?

 

[DRII]

the dealer sent their maintence schedule and there was a graph/check-list that had spark plugs checked at 37.5K...

 

[Joleat]

I bought mine from RockAuto. It was under $30 shipped for six SP534s. There are several 5% off coupons floating around on the ol' interweb. It isn't much savings if you're just buying plugs, but I went ahead and snagged an oil filter, an air filter, and a cabin air filter while I was at it, so the coupon code paid for shipping. I now regret not ordering a 3-bar MAP at the same time. RockAuto has them for around $80, so I could have saved a few more bucks.

 

[mjhpadi]

I think I am going to have mine replaced with SP534's at the next service. May do it myself and let the dealer change the transmission and differential fluid since service would be at 30K miles.  But it looks like the plugs that most have pulled lately look like they are in decent shape for the miles.  I know when I changed the plugs in my F-150 at 75K miles I was really surprised how good they looked...I guess it's the benefit of unleaded fuel...again, dating myself, I remember the old days when plugs got changed every 12K miles and they were really beat up at that mileage.

 

[Brucelinc]

The plugs are looking good - in that there is no fouling or evidence of poor combustion.  However, there is pretty significant erosion of the electrodes.  We are seeing gaps over .040 and stock was .035.  I would change them if you have more than 50,000 miles for sure.

 

[kbeck59]

I changed out the original plugs this morning at 17800 ..

Replaced them with NGK  Iridium ix  LTRR71X-11 stock # 6510  gaped them at .030

Originals were .034 to .038


Ford plugs pulled below..

 

[DRII]

is changing the plugs out basically the same as a tune up?

the dealer is asking the same price, around $300...

 

[SHOdded]

The old plugs look good, SR!  Any diff with the new ones right off the bat?

DRII, do they offer even tuneups for computerized vehicles these days?  I know they sell plug changes or fuel injection system cleanings for around that much ...

 

[kbeck59]

The old plugs look good, SR!  Any diff with the new ones right off the bat?


I honestly can't tell the difference  , just wanted to be good to go for higher boost later .

 

[SHOdded]

True, hasn't been long enough to cause noticeable degradation in performance.  Would be nice tho to get a bump in mpg

 

[DRII]

The old plugs look good, SR!  Any diff with the new ones right off the bat?

DRII, do they offer even tuneups for computerized vehicles these days?  I know they sell plug changes or fuel injection system cleanings for around that much ...

well, it seems to be only a 30 min job.  i wish i were comfortable doing it my self.  I know a car guy whose great at all things mechanical.  i'll see him tomorrow about it...

 

[kbeck59]

The old plugs look good, SR!  Any diff with the new ones right off the bat?

DRII, do they offer even tuneups for computerized vehicles these days?  I know they sell plug changes or fuel injection system cleanings for around that much ...

well, it seems to be only a 30 min job.  i wish i were comfortable doing it my self.  I know a car guy whose great at all things mechanical.  i'll see him tomorrow about it...

About an hour for me ... the back three are a pain ...

 

[BiGMaC]

I changed out the original plugs this morning at 17800 ..

Replaced them with NGK  Iridium ix  LTRR71X-11 stock # 6510  gaped them at .030

Originals were .034 to .038


Ford plugs pulled below..

WOW... 17K and eaten electrodes... maybe we should be changing plugs sooner

 

[DJE624]

I would guess that's from a combination of the tune and the wider gaps.  Mine were at 35 but I didn't have half those miles.  They could have just been regapped.

 

[kbeck59]

I would guess that's from a combination of the tune and the wider gaps.  Mine were at 35 but I didn't have half those miles.  They could have just been regapped.

I changed out the original plugs this morning at 17800 ..

Replaced them with NGK  Iridium ix  LTRR71X-11 stock # 6510  gaped them at .030

Originals were .034 to .038


Ford plugs pulled below..

WOW... 17K and eaten electrodes... maybe we should be changing plugs sooner

The old plugs look good, SR!  Any diff with the new ones right off the bat?

I fail to see any electrode degradation issues on the old plugs , just a light amount of carbon deposits . As stated by SHOdded as well .

Pic below is a close up of one of the plugs ( all look identical ) and a new un gapped NGK in the rear .

What am I not seeing that DJE624 & BigMac are ?

 

[BiGMaC]

Thanks for the close-up comparison pics... in the original pics it looked like the electrodes were degraded to short pointed stubs... In the closer view they look fine and fairly clean...
You didn't miss anything... just my old eyes and bifocals misleading me.  :blink: