OE NGK plugs from a 2006 4.0 Jeep 204,314 miles!

[y_p_w]

Originally Posted By: Bluestream
Originally Posted By: SirTanon
Originally Posted By: Bluestream
Keeping plugs in this long is nothing but a false economy and it's also extremely hard on your ignition system ...Likely wasted hundreds or thousands of dollars in lower fuel economy


Would you say the same thing if the plugs were iridium, and fuel economy was still excellent even at 200,000 miles on them?
that would depend on the condition and how they looked...200,000 is more than enough use even for iridium

Theoretically a good platinum or iridium electrode could last indefinitely. Of course it won't if the nickel material it's fused to wears away like in the first photo.

 

[The_Eric]

Originally Posted By: Bluestream
Keeping plugs in this long is nothing but a false economy and it's also extremely hard on your ignition system ...Likely wasted hundreds or thousands of dollars in lower fuel economy



I thought I'd update the thread- I chatted with the owner briefly the other day and among others things asked about fuel economy. It came in getting about 9-10 and as of the other day, it's STILL 9-10!!!

This thing does have other issues and codes that need addressed though, but I was surprised that it didn't increase.

 

[y_p_w]

I started to think of what I wrote about the electrode wearing away. The spark causes the erosion, and that tends to follow the path of least resistance, which will be across the platinum tips. I've got a few of the original plug's on my wife's Civic, and the nickel portion of the electrodes are actually in pretty good shape even after over 60K miles.

 

[tig1]

Originally Posted By: maverickfhs
That's awesome and impressive!


Those plugs should have been changed 100K ago. His MPG loss cost the driver many times the cost of plugs. Very poor maintenance.

 

[y_p_w]

Originally Posted By: tig1
Originally Posted By: maverickfhs
That's awesome and impressive!


Those plugs should have been changed 100K ago. His MPG loss cost the driver many times the cost of plugs. Very poor maintenance.

More like 170k miles ago. I'm pretty sure the recommended change interval is around 30k miles for normal service. I thought they work like new until the edges start rounding off.

 

[The_Eric]

Originally Posted By: tig1
Originally Posted By: maverickfhs
That's awesome and impressive!


Those plugs should have been changed 100K ago. His MPG loss cost the driver many times the cost of plugs. Very poor maintenance.


That's the kicker... the MPG hasn't gone up! Wild.

 

[Tman220]

Originally Posted By: Danno
Originally Posted By: oldhp
WOW.....I wonder how many times they fired??? Looks like the old side gap plug trick back in the day using the Accel "Big Yellow" Super Coil.

Assumptions:
1250 = average rpms for a mile over the 204,314 miles - assumes some idle time.
6 cylinders
1250/6/2 (4 cycle) = 104 firings x 2 for this engine firing cycle = 208 per cylinder.

208 x 204,314 miles = 42,497,312 firings per plug

Feel free to check my math.


I think you are grossly underestimating..

according to common options for that year it probably has the 4spd automatic with a 4th gear of .69:1. If it has the smaller tires it has a rear end ratio of 3.06. The smaller tire option equates to about a 27.5" tall tire which is about 733 Revs per mile.

So in top gear... 733 X 3.06 X 0.69 = 1548 engine revolutions per mile MINIMUM

Now, its very unrealistic to assume that it spent its entire life in 4th gear to achieve that 204,000 miles. I've had a couple vehicles that have hour meters in them, and I accumulate miles at a similar rate, one of my last vehicles I got rid of at about 195,000 miles, the hour meter in that truck showed about 5200 hours, So that's a lifetime average speed of 37.5 MPH.

So now another assumption, since the average speed for its lifetime is most likely much less than 60 MPH (lets assume 37.5mph) This truck would be in 3rd gear at 37.5 mph which is 733 X 3.06 X 1.00 = 2243 Revs per mile average. This accounts for revolutions of the engine at idle, 1st gear, 2nd gear, 3rd etc.

So if this 4.0 uses a waste spark system then each plug will fire every time a piston hit Top Dead Center, so each plug fires once for every engine revolution. So lets put this together.

revs per miles = 2243 multiply by the mileage 204,314 miles should equal the approximate firings of each individual plug
2243 X 204314 = 458,276,302 firings!

 

[The_Eric]

Originally Posted By: Tman220
Originally Posted By: Danno
Originally Posted By: oldhp
WOW.....I wonder how many times they fired??? Looks like the old side gap plug trick back in the day using the Accel "Big Yellow" Super Coil.

Assumptions:
1250 = average rpms for a mile over the 204,314 miles - assumes some idle time.
6 cylinders
1250/6/2 (4 cycle) = 104 firings x 2 for this engine firing cycle = 208 per cylinder.

208 x 204,314 miles = 42,497,312 firings per plug

Feel free to check my math.


I think you are grossly underestimating..

according to common options for that year it probably has the 4spd automatic with a 4th gear of .69:1. If it has the smaller tires it has a rear end ratio of 3.06. The smaller tire option equates to about a 27.5" tall tire which is about 733 Revs per mile.

So in top gear... 733 X 3.06 X 0.69 = 1548 engine revolutions per mile MINIMUM

Now, its very unrealistic to assume that it spent its entire life in 4th gear to achieve that 204,000 miles. I've had a couple vehicles that have hour meters in them, and I accumulate miles at a similar rate, one of my last vehicles I got rid of at about 195,000 miles, the hour meter in that truck showed about 5200 hours, So that's a lifetime average speed of 37.5 MPH.

So now another assumption, since the average speed for its lifetime is most likely much less than 60 MPH (lets assume 37.5mph) This truck would be in 3rd gear at 37.5 mph which is 733 X 3.06 X 1.00 = 2243 Revs per mile average. This accounts for revolutions of the engine at idle, 1st gear, 2nd gear, 3rd etc.

So if this 4.0 uses a waste spark system then each plug will fire every time a piston hit Top Dead Center, so each plug fires once for every engine revolution. So lets put this together.

revs per miles = 2243 multiply by the mileage 204,314 miles should equal the approximate firings of each individual plug
2243 X 204314 = 458,276,302 firings!


You know I never bothered to look into the math on that, but since you've brought it up, the Jeep is a rural mail carrier Jeep and had been all it's life. So this thing gets driven hard! I'm talking stoplight to stoplight (or mailbox to mailbox if you prefer) racer hard. Also one of the few things that is still wrong with this Jeep is the rear diff is out of it due to water intrusion... I serviced it and while doing that, I looked at the I.D. tag so I could get an accurate quote- It's a 3.73:1 rear and it has about a 31" tire on it.