11

When heading to the store to pick up a new set of spark plug wires, I found three products at this particular shop:

  • Product #1:
    • Price: Cheap
    • Boots: EPDM
    • Core: Suppression
    • Insulation: EPDM
    • Max Temp: 356F
  • Product #2 (labelled "Gold Series"):
    • Price: 2x Product #1
    • Boots: EPDM Top, Polyester Tube, Silicone Tip
    • Core: Suppression
    • Insulation: Silicone
    • Max Temp: 482F
  • Product #3 (labelled "High Performance"):
    • Price: 4x Product #1
    • Boots: Silicone
    • Core: Spiral
    • Insulation: Silicone
    • Max Temp: Unknown, but presumably high given silicone use

Electrically, these just all seem to be wires that move electrons around and successfully fire the spark plugs, all presumably large enough to handle the required currents, all presumably with resistances in an appropriate range.

Product #3's description states (emphasis mine):

[These] wire sets utilize a construction method known as "variable pitch" wire winding to create resistance to radio frequency interference. They have a lower resistance than conventional carbon core wires, which translates into longer wire life. At the center of each wire is a fiberglass stranded core, made from the same family of materials as those used in bulletproof vests. This core greatly enhances the overall strength of the wire and prevents the pulling strains that wires are often subjected to. They feature custom-designed terminal boots that provide an exact fit and high-quality EPDM and silicone coverings to resist high temperatures, oil, and chemical damage. Each wire is fitted with a positive-locking, corrosion-resistant, nickel plated terminal end for a tight fit and maximum resistance to vibration and separation.

So my questions are:

  1. Do "high performance" spark plug wires affect how the vehicle runs in the short term and, if so, how? I can't imagine what effect the wires could possibly have but their marketing departments have successfully kicked me into full consumer-mode and hooked me with the word "performance" and a high price point.
  2. In any case, it seems like the major difference is simply durability, given the description of product #3. Is this true, and does this justify the extra cost (e.g. if an expensive wire has an expected lifetime less than 4x a cheap one, but costs more than 4x more, why would I buy it)? I imagine even the cheapest will last many tens of thousands of miles or more, though.
5

There isn't any performance to be gained from spark plug wires, just better build quality, which gives you not a better spark, but rather maintains an appropriate spark for more miles/years before their performance degrades to the point of needing replacement.

You cannot tell build quality by reading the side of a box, it is a manufacturer reputation more than anything else. I recently had to replace spark plug cables on one of my vehicles and had to choose between a few unknown brands at half the cost of a reputable brand. I went for the reputable brand because I trust them.

  • For the low end, cheapest wire sets, do you feel that their expected life time is short enough to be a noticeable pain? E.g. would it be unusual for cheap ones to fall apart more often than, say, the spark plug change maintenance interval (105,000 miles for my car)? – Jason C Jul 14 '16 at 1:34
  • 1
    Spark plug cables can go bad without necessarily falling apart, and it's not that they will suddenly stop working when they're done. They will intermittently stop delivering spark, making your engine miss a beat, and there's about a dozen different things that have the same symptoms. in my neck of the woods, the cheapo-branded wires were only half the price of the name-brand ones, so I went with the name-brand ones based on their quality reputation. I don't gamble with ignition parts. – tlhIngan Jul 14 '16 at 6:14
  • 1
    @JasonC At the end of the day a cable is a cable. It supplies electrical potential energy from a source to a destination; spark plugs are somewhat exceptional as they work at anywhere from 12,000-45,000 volts, so any minor defects in the conductive material may cause problems further down the road after plenty of use. – Trotski94 Jul 18 '16 at 10:06
5

Here's an article that explains spark plug cables. It had some interesting information that I hadn't really thought of.

That said, I'd say the largest difference in consumer grade spark plug cables will be on durability. It will probably have a bit of better electrical traits (e.g. resistance), but I don't imagine you get a large gap in spark performance until you hit the purpose built ranges. Finally, I've personally never installed "performance" spark plug cables, but I have installed cheapo ones and had them start to fall apart within 2 years (which was WAAAAY faster than I expected). Few things have made me more frustrated than having to pry the terminal boot off a spark plug since it ripped off the cable.

So, unless the difference and overall costs are high enough to burden you, I'd personally get the mid or high "performance" ones. But that's largely based on the bias of my individual experience with 1 (probably faulty) product.

  • From the way you talk about it, it seems that even if a 4x expensive wireset doesn't last 4x longer than the cheap one, you still think it's worth the cost to avoid major fall-apart hassles liked ripped wires and such, yeah? Interesting article btw, thanks for the link. – Jason C Jul 14 '16 at 1:36
  • Personally I may get the 4x model. Depends on overall cost mostly. – kyle_engineer Jul 14 '16 at 1:59
  • And what other affects are advertised. – kyle_engineer Jul 14 '16 at 2:00
3

As @tlhIngan said, the benefit of good wires isn't so much the quality of the spark when they are new, but the longevity of the wires. Spark plug wires don't lead an easy life, they are exposed to high temperatures and high voltages and a lot of strain and bending during plug changes and other work around the wires. As they start to fail they will become intermittent and some of the spark energy will be dissipated by "leaks" through the insulation to any grounds that can be found. That's likely to lead to reduced fuel economy even before you notice it as missing. So the cost of good wires may repay itself in ways beyond just longevity of the wires themselves – you may get some of it back in savings on fuel costs, and also in troubleshooting time as well.

With any wires, it helps to keep them clean and to avoid sharp bends and chafing. Wires with a carbon (suspension?) core can fracture if they are bent sharply leading to intermittent misses, and insulation that is dirty or damaged is more conducive to "leaking."

3

From many years of selling both 'standard' and 'high-performance' HT lead sets, here's my advice:

If you're replacing your lead set because it's simply time to do so, buy the cheap ones: they're perfectly ok for most 'normal' applications.

If you're replacing them because the last ones gave trouble after less than expected mileage, go for the #2 mid-range ones. They're stronger, that's about all.

If you're racing, or driving a high-performance vehicle, buy the high performance ones for the simple fact they can handle higher temperatures.

In all truthfulness, most of the 'high performance' is about marketing. The silicone is high temperature, the fiberglass core simply prevents you from breaking the wires by pulling on them - which is bad practice anyway.

From a car parts salesman's point of view, buy the dearest ones ($$$ ka-ching! $$$) From a mechanically savvy car-owners point of view: save your self the money.

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