427HISS; There is a lot to consider when talking about this subject. One major thing to keep in mind is the difference between lab findings, and real world engine conditions. First, let us assume all parts of the ignition system are operating properly.
Considering the new rare earth metals used in electrode tips...YES, they do last longer than standard metal tips...but does that matter in an FE powered vehicle? I don't think so.
A few parameters a spark plug must meet are, correct heat range, correct spark gap, the ability to thread in and fit the hole as intended, the ability to arrest the spark energy and channel it to the plug gap only, and the ability to properly hold the spark plug wire...The rest is some sort of add on.
An Autolite 45 is a pretty standard plug for FE engines, and has been around for a long, long time. This plug will function properly if it is the correct heat range for the tune of the engine as well as having the correct gap. In a points style system it will easily go 30,000 miles, and in a more modern system it will easily go 50,000 miles.
But, at less than $30 for a set of 8 plugs it really does not matter because they are cheap to replace if something goes wrong.
The V-plugs, and other poly-electrode styles do offer some benefits, but only in terms of more sharp, conductive areas for the spark to jump across.
The electrical properties of the spark are limited to the physics of electricity.
This means the spark will jump the gap of least resistance.
When the single electrode plug begins to wear, the spark must work a bit harder to jump the growing gap. Until the gap becomes more resistive than other conductive gaps, the spark will continue to jump that gap...right up to misfire conditions.
The poly-electrode plugs do provide multiple areas for the spark to arc across, but they do not provide an "easier" area for the spark to arc across until the easiest area wears to the point the spark arc begins using a different gap area than the now worn and harder to jump gap occurs.
In effect, the poly-electrode plugs provide more wear surfaces as compared to a single electrode plug. All else is equivalent when the system parameters are taken into consideration.
The Autolite 45, when gapped correctly and in good condition, will provide the same spark, across the same .040" gap, as any other quality conductor capable of handling the power of the system.
The poly-electrode plugs do provide a "better" life in systems, or uses, that tend to burn electrodes quickly simply because they literally have more electrodes to burn down before the plug begins to misfire.
This same principle occurs in the rare metal tipped plugs. The tips simply last longer and therefore maintain the proper gap longer...but they do not provide a better spark across a given gap.
The rare earth metal tipped plugs do present a potential to lose the tip...They are affixed in some manner so they will come off at some point. This VERY hard tip now must travel through the system until ejected out the exhaust, or becoming lodged into some portion of the engine where it finally resides.
My findings concerning spark plugs are this.
1) The plug must be constructed properly, Good threads, good seal washer if required, good porcelain (resistor/insulator) good conductor and connection to the plug wire tip, electrodes that maintain the set gap, proper length of plug body into combustion chamber for the application.
The rest, while verifiable in the lab, probably does not result in increased performance with normal engine use.
Last is the general use of most FE engine these days. While many FE's now reside in nice cars and trucks and boats, few of them see daily use and high miles each year...Many don't see 3,000 miles per year.
This means a lowly 30,000 mile lifespan spark plug will probably last 8-10 years in most instances when screwed into an FE engine these days.
Find a spark plug you like, understand, and have verified as a working heat range for your engine tune and let the rest work itself out.
If there is one thing I have verified over the decades in terms of spark plugs it is this.
I have never, ever, had a properly sized, name brand, spark plug NOT work properly without a good reason.
That reason is usually a physical defect in the plug, some issue with the ignition system of the engine, a poor tune, or some variation of all of these...but never has the plug itself been the problem.
Champion, Autolite, Motorcraft, NGK, Bosch, AC Delco, Denso, they all work well when applied, gapped, and installed correctly.
