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Life Expectancy Of Spark Plugs


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#1
aj3983

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how long can i expect the current stock spark plugs to last on a 02 v6? already have 41k. if i get the v-power and new iginition wires how long will they last? or am i just being really anal retentive :wub:

#2
Trebuchet03

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12K miles is recomended. Most have success with OE NGK plugs/wires.

From manual:

A normal set of spark plugs usually requires replacement after about 20,000-30,000 miles (32,000-48,000 km), depending on your style of driving. In normal operation plug gap increases about 0.001 in. (0.025mm) for every 2500 miles (4000 km). As the gap increases, the plug's voltage requirement also increases. It requires a greater voltage to jump the wider gap and about two to three times as much voltage to fire the plug at high speeds than at idle. The improved air/fuel ratio control of modern fuel injection combined with the higher voltage output of modern ignition systems will often allow an engine to run significantly longer on a set of standard spark plugs, but keep in mind that efficiency will drop as the gap widens (along with fuel economy and power).

Platinum tipped spark plugs usually require replacement after about 50,000-60,000 miles (80,000-8,000 km). However, some manufacturers have recommended replacement at 12,000 miles (160,000 km).



But if you have problems, the plugs last $2 long (or however much you paid).

#3
jjbyrd

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I don't understand the 12k miles reference (last sentence - I think that ref. was supposed to read 120,000 miles / 160,000 km). 20k miles is pretty much it for standard plugs, but you still need to check them for gap at a couple intervals. Platinum/Iridium stuff was made to go 50k to 60k without re-gapping because of modern applications where you have to cut the car in half to convieniently change or re-gap your plugs.

Changing plugs and wires at 60k will coincide with your need for a new timing belt, if nothing goes amiss. NGK plugs/wires are very nice and highly recommended.

#4
aj3983

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so i can wait till i hit 60k before i need to change the plugs and wires? the stock plugs can last that long.

#5
Trebuchet03

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I don't understand the 12k miles reference (last sentence - I think that ref. was supposed to read 120,000 miles / 160,000 km).

Its supposed to be 12K miles. That goes with the annual tune-up deal. The reasoning for that is simply efficiency. You could go 20K miles, yes. but because of the relative low cost, might as well do them when you're doing the rest of your annual maintnence. If you don't change them, you def. should have the gap reset.

Platinum/iridium are great, they last a long time. But copper conducts better, and you cant file down platinum plugs to get a crisp edge. I'd rather save the money and buy new plugs every year (for the 6 cyl, you're looking at $12 for a new set of plugs B) ).

#6
aj3983

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thanks for the help guys :biggrin:

#7
jjbyrd

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I'm pretty comfortable saying that 12k on Platinums is a silly number. Trebuchet03, you quoted a manual, so let's stick with it for a sec. Read that last ref. sentence in italics slow... They say "replacement at 12,000 miles (160,000 km) "... 160,000 km converts to 120,000 miles, NOT 12,000 miles! It's a typo - really really! The italics part is about Platinums, not copper. Buying $2 plugs every year wouldn't really save you money if you ran platinums for the 4-5 years it might take to get to 60k miles. But, if you like changing plugs, go for it - you can't hurt my feelings! I will continue to be confused though, if you stick to giving advice with the 12k number for replacing platinums (or even copper, which will go 20-30k - or at least 2 years by your schedue). -_-

If I ran a performance engine with nasty ole' points/condenser ignition, I might do an annual tune-up with new copper plugs and agree with your 12k business. The 626 is none of those things. OEM says 60k miles. Your italics ref. says 120k miles. I'd be happy to get to 60k and change out, provided there are no signs of trouble. Good plug wires will go to 60k as well.
...trying to not make it harder than it needs to be.
Good luck. B)

#8
Trebuchet03

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^^ :lol:

Haha, we're talking apples/oranges. I've been talking copper plugs (the platinums never worked well for me :huh: ).

As far as savings... if the engine conditions were exactly the same at all times for both types, yes its cheaper for the plats. However, Copper is the best conductor in this case :huh: Better=spark = more complete combustion = better fuel economy :huh:

<Thanks for pointing out the typo :P > The 12K for copper is just my personal number. I've just had excellent results (I change once per year, 12-15K miles, and regap every 6 months) :huh:

#9
jjbyrd

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B) I'm all better now...

#10
jjbyrd

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Rabbit food for thought (not to split any hares)... All platinum plugs are a plating or tip treatment only, they often have copper cores (in the case of NGK - others may be steel cored, etc...) Some that are 'tipped' can be filed, use a diamond nail file gently so as not to leave any steel bits on your platinum (check with mfr.). Platinum is there for corrosion resistance, and to make the plug easier to fire with a larger gap / bigger spark kernel (yup, lower resistance, better conductor, less fouling, better ignition event). -_-

Copper core and tips offer MORE resistance which actually can form a stronger spark when it finally arcs (i.e. more voltage required to jump the arc = more energy in the spark itself), BUT only if your ignition is strong enough to light them off - every time, without misfire, all the way to red line. Oddly enough, filing a copper plug to a 'crisp edge' makes it easier to jump the spark too, thus lowering its spark energy a bit, just like platinum plugs... hmnmnm... Yup, the shaping on the Vpower plugs (splitfire,etc) makes it easier to fire the plug too.

How do you take advantage of all these 'easy to fire' plugs? Set the gaps wider (at least opened up to the OEM gap), which again makes it harder to fire (increasing spark energy) AND makes a bigger spark/flame kernel (as long as you avoid misfiring AND don't have the plugs bumping your piston on the way up!). A big, high energy flame kernel, timed correctly and well exposed to the combustion chamber is the way to gain hp from a plug. In quest of large flame kernels and fast/efficient ignition events, some race engines run 2 plugs in each cylinder. I've even seen a 3 plug set up.

and those OEM folks can be pretty crafty sometimes...

#11
Trebuchet03

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I dont understand where you say platinum is a better conductor...

I'm looking at my tables and I'm seeing a 6X difference between copper and platinum :huh: For that matter, Irridium is 2X better electrical conductor than platinum and even more rare :P


As far as the crisp edge thing, for anyone interested, the reason why that happens is because electrons will gather around sharp edges (such as a plug edge or corner).

I think its turned into a plug design discussion rather than longevity :P

#12
aj3983

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if the stock plugs last so long how come you guys dont use them more and what brand and model are the stock ones?

#13
jjbyrd

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We started off by advising someone that plugs last 12,000 miles max (half the typical/reliable life of good copper plugs) by the apparent authority of misquoting a manual and finally saying "its my personal number"?! I guess you can't hurt anybody by this advice, and of course they'll work well for you by doing this, but why the unnecessary expense? I replied because this advice seemed strange.

My apologies to all if I got carried away, but my info is good... as for the science, its the resistance to arc... the resistance to jump the gap and make a spark... not conductivity of some wire on a bench at room temperatue. I seem to be out of breath here, so please, please try some research on like NGK's website or some other reasonable authority.

Maybe we could take a survey and see who is using what plug?? I hear mostly about NGK on this site.

aj3983, if your OEM plugs are platinum they are designed to go about 60k miles and will do so normally, if copper then 20-25k miles. I sort of recal OEM might have been NipponDenso, but I'm not sure. I like NGK's, you'd be fine with any of their products recommended for the 626, NipponDenso would be my second choice. I have been avoiding Bosch (my old favorite) due to bad experience(s). Platinum or copper is your choice, depending on how often you want to change them...

#14
snailman153624

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I dont understand where you say platinum is a better conductor...

I'm looking at my tables and I'm seeing a 6X difference between copper and platinum :huh: For that matter, Irridium is 2X better electrical conductor than platinum and even more rare :P


As far as the crisp edge thing, for anyone interested, the reason why that happens is because electrons will gather around sharp edges (such as a plug edge or corner).

I think its turned into a plug design discussion rather than longevity :P

I think what he meant is platinum is a better conductor in practical use, because it doesn't build a layer of oxidation like copper (or most other metals for that matter) does. Sure, in theory copper is one of the very best conductors, but that's pure copper.

As mentioned, platinum and iridium is just a coating. These in my experience fail around 95k miles.




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