Spark Plug Question

Kirk · Jun 6, 2008

All the newer rides of the last 10 yrs or better say that you can go 100K between tune ups (ie spark plugs). I'm having a hard time buying that. It seems in the "old days" we used to change plugs every 30K or so. Can you really go that long without performance/mileage suffering? How often do you guys change you plugs and what plugs do you use?

Big Jim M · Jun 6, 2008

I have found the newer engines with fuel injection and unleaded fuel to run in excess of 100K on every part in the vehicle.
My 2001 Suburban has 160,000 miles on it. I changed the plugs and wires at 125K and it was running good at the time. There was NO difference in milage or performance after changing the sparks.. I just installed the third set of tires on it. It has the ORIGINAL brakes still on it... I did change the fuel pump and the thermostat at the same time..But they were working fine also at the time.
As for the tranny and the radiator? Never have touched them either..
It seems to me that TOYOTA and the other imports have taught quite a bit to our big3.
Big JIm

Bob Ayers · Jun 6, 2008

With the platinum electrode plugs, they should run 100K miles with no problem.

Here are a couple pictures, of a new Motorcraft double platinum plug, and one that has run 50K miles:

krugford · Jun 6, 2008

While I don't doubt the fact that you can go 100k on a set of plugs, I wouldn't want to have to pull those plugs out of an aluminum head after that long. I've two seperate vehicles takes the threads with it..

Bob Ayers · Jun 6, 2008

krugford said:
While I don't doubt the fact that you can go 100k on a set of plugs, I wouldn't want to have to pull those plugs out of an aluminum head after that long. I've two seperate vehicles takes the threads with it..

Good point! I wouldn't recommend leaving them in cast iron heads for 100K miles either! Remove them every 40K to 50K miles, and intall them with a little anti-seize grease, and plenty of dielectric grease in the plug wire boots.

fixizin · Jun 6, 2008

I'm about to change plugs and wires.

Most new wire+boot sets are preloaded with silicone grease, but what are some brand names of the "ANTI-SEIZE" compound/grease to use on the threads??? :dntknw:

Bob Ayers · Jun 7, 2008

fixizin said:
I'm about to change plugs and wires.

Most new wire+boot sets are preloaded with silicone grease, but what are some brand names of the "ANTI-SEIZE" compound/grease to use on the threads???

Here ya go, I normally use the first one on spark plugs:

Temps -60F to 1600F:

http://www.permatex.com/products/Au...ubricants/Permatex_Anti-Seize_Lubricant_a.htm

Temps -30F to 1800F:

http://www.permatex.com/products/Au...ts/Permatex_Copper_Anti-Seize_Lubricant_b.htm

Temps up to 2400F:

http://www.permatex.com/products/Au...auto_Permatex_Nickel_Anti-Seize_Lubricant.htm

shadetree · Jun 7, 2008

Many new plugs already have anti-sieze on the threads. Also, if you use too much silicone in the boots, they can form a vacuum and be damned hard to remove. In most cases when this happens, you have to have a tool to pull the boot from the side. Use the grease sparingly. shady

Bob Ayers · Jun 7, 2008

shadetree said:
Many new plugs already have anti-sieze on the threads. Also, if you use too much silicone in the boots, they can form a vacuum and be damned hard to remove. In most cases when this happens, you have to have a tool to pull the boot from the side. Use the grease sparingly. shady

No, normally the boot will pressurize and pull the connector off the plug.

shadetree · Jun 7, 2008

Bob Ayers said:
No, normally the boot will pressurize and pull the connector off the plug.

You don't know what you are talking about. Not all boots are the same, and not all engines are the same.

Once you relieve the pressure so the boot will slide down over the plug and stay on, it then creates a vacuum in some cases if you try to pull the boot back off, more especially if the boot is new.

When you have pressure to overcome when replacing the boot back over the plug, I have found that too much grease was used. If it will form pressure, it will form vacuum. I have done this several times, so I damn well know what I am saying. If you had any hands on experience other than your own vehicle I would give your advice some credibility, but since you don't....... For some insane reason you think you are some kind of spark plug guru, but I for one am not impressed. shady

Will · Jun 7, 2008

I assume that since you generally squeeze the boot when you push it on, the air comes out. Good for the boot. I don't fool with plugs anymore so more power to it if it doesn't want to come off.

I have never changed the plugs on my 4.0, which I bought in 2001. Since the EFI motors run so well, the plugs don't foul or get blistered from heat like the last edition of lean-burn carb motors did. About the worst thing that happens is the edge gets rounded off and theoretically the spark can't jump off as readily--but the juice these ignitions put out is a lot more than an old single point motor that had limited ability to saturate the coil primary. As far as plug wire--check them with an ohmeter before simply replacing them. There's never anything to be gained by replacing good parts.

shadetree · Jun 8, 2008

Will said:
I assume that since you generally squeeze the boot when you push it on, the air comes out. Good for the boot. I don't fool with plugs anymore so more power to it if it doesn't want to come off.

In some cases, especially on the bigger boots, if you get too much silicone the boot is hard to press on as it traps air inside. If you turn it loose, the trapped air will push the boot back off. If you force it on, and push the air out, it will have vacuum if you need to take it back off. The newer boots, especially the good ones seal very well, and all you need is just a little lube to get it to slide nicely over the plug. I have a tool I made for removing plug wires so that I don't pull the wire out of the boot when removing it from the plug. The ones that always give you trouble are the ones that you can barely get to.

I agree on replacing good parts. shady

fixizin · Jun 8, 2008

Will said:
As far as plug wire--check them with an ohmeter before simply replacing them. There's never anything to be gained by replacing good parts.

That's a good point, but my wires are 9 years old, and filthy... (OTOH, only 33k miles)... still, when I look under the hood at night, I see no arcing, hear no RPM buzzing on the AM radio. SO...

a) what to safely CLEAN the wires with?
b) my Chilton's on CD has a go/no-go value, for ohm'ing the plug wires, of 7,000 ohms/ft., but what say ye forum RKIs?

One of my plugs already had the electrode break deep inside (boot pulling up too hard from "vacuum"??... or just a freak plug?), so I figure replace the other 5 as well--Autolites aren't that spendy. They look like the OEM plugs, and I don't think either is platinum. Probably replace 'em again in 30-40k mi.

Bob Ayers · Jun 8, 2008

Will said:
As far as plug wire--check them with an ohmeter before simply replacing them. There's never anything to be gained by replacing good parts.

Measuring the end to end plug wire resistance will tell you if the center conductor is continuous. It will not, however, tell you if the insulation has
broken down, causing spark leakage to GND, which will also cause a misfire.

Bob Ayers · Jun 8, 2008

fixizin said:
They look like the OEM plugs, and I don't think either is platinum. Probably replace 'em again in 30-40k mi.

The OEM plugs are 2 different P/Ns. The GND electrode is platinum in one bank, the center electrode is platinum in the other bank (each is single platinum). This is due to 2 plugs firing together in series, and each plug
receives the opposite polarity spark.

Here is a schematic I put together showing Ford's EDIS coilpack for a V-6:

The plugs also fire every revolution of the crank, twice as often as a conventional ignition.

Spark Plug Question

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