One of the Worst Selling Points, New Vehicles

[Chispas]

Owner's manual says 100,000 spark plugs... BUT they don't say they need to be re-gapped about every 30,000 miles... Big gasoline waste if they're not...

 

[cousincletus]

My biggest fear was getting the plugs out of the head at 100K, but they apparently use aluminum-friendly metal in the new spark plugs or antiseize (GM). FWIW I replace the plugs at 60K and the gap doesn't look too bad.

 

[bretfraz]

How much gas is being wasted if they're not regapped? What kind of MPG boost can I expect if I regap every 30K? What is the MPG drop if I don't?

 

[mechtech]

If the Mfr. recommends those long intervals, the plugs are precious metal tipped, and shouldn't need regapping at 30k.

 

[BUBBA0420]

If they recommend 100,000 on the plugs those plugs are Iridium tipped and are not supposed to be re-gapped.

 

[Schmoe]

New plugs are recommended at the 106K mark on my 02 Accord. I took them out and looked at them and boy, you couldn't tell if it had 30K on them or 100K. Amazed me.

 

[eljefino]

Wider gaps better ignite lean fuel mixes. If they misfire the computer complains before you even feel it. Agree with the fear of siezing in the head though.

 

[wantin150]

quote:

---

Originally posted by BUBBA0420: If they recommend 100,000 on the plugs those plugs are Iridium tipped and are not supposed to be re-gapped.

---

The need to gap iridium plugs is up for debate. Some camps say that since the wire is so fine, you shouldn't gap or you run the risk of breaking the electrode. Other camps say you should, using a special tool. My particular car has a spec'd range of gap and the NGK Iridium IX plugs come in within that range so there is no need to gap them. I would trust the "100,000 tune-up" very little. I think that after that long in the engine, there is always that risk of them seizing. If anything, loosen, remove, and re-torque every 30-50K and you should be OK. I changed my iridium plugs at 50K and wouldn't have wanted to run them much longer based on what they looked like. (No, no fouling or damage or anthing like that, just the electrode appearance).

 

[gtx510]

quote:

---

Originally posted by BUBBA0420: If they recommend 100,000 on the plugs those plugs are Iridium tipped and are not supposed to be re-gapped.

---

OEM plugs are mostly platinum and not iridium. Ir has 1/2 the resistance of platinum. I've heard that shouldn't matter but i don't believe it. And it's only one element down so it should wear about the same. I replaced the stock plugs on our BMW 530i at about 80k. They were 4-prong NGK platinums and the center electrode was done. Regapping them helped a bit (very tough with 4 electrodes), but replacing them with large gap Ir plugs really helped. Smoother idle, better throttle response, less raw fuel smell during cold starts. I didn't keep track of the mpg's very well as it's not my car but I believe they went up about 1 mpg. 15 to 16mpg, yoohoo. this site has some Ir info: www.sparkplugs.com/faqmain.asp

 

[Master ACiD]

most if not all plugs today come right out of the box with a plating on the threads that acts as an anti-seize.

 

[Kestas]

quote:

---

Originally posted by gtx510: Ir has 1/2 the resistance of platinum. I've heard that shouldn't matter but i don't believe it. And it's only one element down so it should wear about the same. I replaced the stock plugs on our BMW 530i at about 80k.... I didn't keep track of the mpg's very well as it's not my car but I believe they went up about 1 mpg. 15 to 16mpg, yoohoo.

---

I imagine more than one material property is considered for plug tip material. - melting point - oxidation resistance - electrical resistance - cost, fabricability Pt and Ir have very migh melting points. There are many other elements with even higher melting points - Mo, Cr, Si, C - but they would quickly oxidize. Spark plug choice, per se, doesn't increase gas mileage. Otherwise, the manufacturers would simply specify better plugs to achieve an extra 1 mpg (which is a lot in today's competitive market!). New spark plugs will only increase gas mileage if the old ones weren't igniting the mixture.... and that happens when the old plugs are dirty or misgapped. Premium plugs are offered in the market simply to extend the length of service of the plug in the engine before replacement.

 

[MADMIKE]

These precious metal-tipped plugs don't need re-gapping. The whole point of using these specific (and expensive) metals is to avoid "gap erosion" requiring plug replacement or the cheap and temporary fix of closing the eroded (widened) gap back up by re-gapping the plug.

 

[gtx510]

Trust me at 80k the center electrode was fairly well eroded, completely rounded off. And it doesn't project out of the insulator much so it was wearing down into the insulator. I wish i could've gotten close-up pics but my camera couldn't handle it. Regapping was just a temporary fix until I could find new plugs. Kestas, I mentioned resistance. I think Ir (or the alloy that is used) also has a higher melting point than plat. more resistant to oxidation too? Cost came down a few years ago where they figured out the Ir alloy? Before that NGK was selling gold-pallidium fine-wire plugs, I still gotta set of those.

 

[OriginHacker21]

Off Topic: So on average with new'er cars (2000+) you all recommend changing spark plugs at 50-80k? How to find out what type of spark plugs your car came with? (2004 Pontiac Sunfire). Regarding MPG - when I bought my car (2004) at 6,000 miles I averaged 35MPG. Today at 57,000 miles I'm averaging 36-37MPG. I've never done anything to the engine so the spark plugs must not be losing much MPG. Looks like I will get them replaced soon tho (within 10k).

 

[Schmoe]

quote:

---

Originally posted by Master ACiD: most if not all plugs today come right out of the box with a plating on the threads that acts as an anti-seize.

---

You don't want to put antiseize on Ford 5.4 engine made between 00 and 04, the ones with only 4 threads in the head for the spark plugs. They have a bad history of blowing out.

 

[JHZR2]

When my 98 S10 ZR2 hit 50k, I decided to pull the plugs to see what they look like. They are 100k platinum plugs, but, though they are tougher to do than an I4 - they were easy to pull and I had the tires off anyway, so why not... They looked identical to the replacement delco platinums I bought to put in. gap was 100% OK too! I put the new ones in, but kept the originals... maybe Ill wash them in solvent and put them back in as 'new' in 50k! JMH

 

[Kestas]

quote:

---

Originally posted by Schmoe: You don't want to put antiseize on Ford 5.4 engine made between 00 and 04, the ones with only 4 threads in the head for the spark plugs. They have a bad history of blowing out.

---

I don't see how antiseize would help the plugs blow out. The blow-out problem is from the threads in the cylinder head getting buggered up by the carbon that collects on the exposed threads. When you go to remove the plugs, the built-up carbon deforms the threads, leaving the next set of plugs with less purchase on the threads, thus rendering the next set of plugs vulnerable to popping off. Go ahead and use antiseize on the threads.

 

[UncleS2]

If I bought a nice new car with 100,000 mile specified plugs in it, I'd probably run 'em for 100K & only pull 'em if something seemed wrong- that includes gas mileage. Why? *Way* back when the Neon was still under warranty, it spit up a storm when started one muggy humid morning, & check engine light came on & would not go off. I took it back to the dealership, they checked it on the computer, & the mechanic's worksheet said he pulled the plugs, checked gap, re-installed. That was at ~30,000 miles. The owners manual specs plug replacement at around 35-40 K, I believe. I finally pulled & replaced those original, pulled-once plugs- at 89,988 miles! They still started & drove fine, only missed at nearly 6000 rpm or above. What were those near-miracle plugs? Plain old Champion copper-core factory installed cheapies: RC9YC. So if they say a new set of iridiums will go for 100k, I'm willing to give it a try.

 

[Winston]

There was an interesting technical article about the developement of the Iridium spark plug. Lots of charts comparing it to Platinum plugs. Clearly, the Iridium will last longer than the Platinum. There is also a version of Iridium with a finer electrode that makes a better spark than the Long life version. The point with gapping Iridium or Platinum spark plugs. It is OK to carfully check and adjust the gap upon installation of the new plugs. However, if the gap has changed during use, then the plug should be discarded. If the gap has changed significantly then the Iridium or platinum metal is probably all gone. Thus, the warning, do not re-gap Iridium or Platinum plugs.

 

[Chispas]

When started, there was no idea people thought spark plugs going 100,000 miles.... Wow !