Spark plug wire lifespan and plug question

My Focus has been idling a bit rough and I finally realized my plugs and wires are like 8 years old. Now in those 8 years I have only covered about 25K miles. I can spend the 30 minutes changing plugs at this point. I was going to throw on some wires too but I was surprise to see most of the prices above $50 for four plug wires. Most google fu returns a lifetime of 60K on wires. What about age?

Also what about copper vs platinum vs iridium, etc... any real difference beyond lifetime? No, I don't think I will have this car for another 70K.

Just wondering.

Wires last until they don't work anymore.  In a Focus motor, that can be a huge range. The valley the plugs are in finds water, so if it's dry, they will probably be fine.  Pull the plugs and check for carbon tracking on the ceramic.  If the plug has a track, the wire does as well, and needs to be replaced.  As for plugs, lifespan vs cost is the only consideration. Gimmicks are gimmicks.  The number of electrodes is moot. Platinums will cost three times as much and last three times longer.

Check on Rockauto for wires. I can get NGK wires for my rotary for $14.95

If the plugs are so easy to change, there is no need to install the expensive plugs.  

My methods to check spark plug wires:

Method 1:  Get a plastic handle screwdriver and a clip lead.  One clip lead to ground, one to the screwdriver metal.  Hold by the plastic.  Run the metal part of the screwdriver over the spark plug wire while the motor is running.  If sparks jump to the screwdriver, that wire is shot.

Method 2:  (requires less tools).  With the motor running, grab each spark plug wire in turn with your bare hand.  If you get thrown across the garage at any point, that wire is shot.

The insulation around the wire core will age out. So plug wire millage is not always a good indicator.  You should test each wire for resistance. Wire length is a part of figuring put proper resistance. 

My take on plugs and wires is that this is one place where going OEM is a very good choice as you know that not only will the parts work with the car but they will also work with each other. 

As far as plugs go, stick with OEM conductor type (irridium, platinum, copper) and keep the electrode simple.  Engineers know that the best spark is a consistent spark.  Having two or three electrodes doesn't help anything or make the spark better, it just makes it jump around to different electrodes.  Keep it simple.

Do a little googling on your specific car.  Even though it shouldn't make a difference about brand, it really does.  Some Hondas won't like anything but NGK or Denso.  My LT1 eats Bosch Platinums every 30k, but they work great in my old E30.  It's an enigma and I can't explain it, but it really sometimes matters.

With wires, I always test resistance.  If they all fall within spec, I'll reuse during a plug swap.  If I see carbon tracking, I'll use dielectric grease in the boot and I haven't had any troubles.

Wire design is important as well.  Many cheap wires are a fiberglass core with graphite in it.  Usually very high resistance, but also very good radio suppression.  The other end of the spectrum is solid core which uses a straight metallic conductor.  Nearly zero resistance, but good luck using the radio or keeping the ECM happy.  In many cases, the middle ground is perfect: spiral core.  Pretty good noise suppression (enough you won't hear it on AM radio and pretty safe for even the most sensitive electronics), and very low resistance.

I also just went back and checked the OP....   Ford almost always equals OEM ignition parts.  Coils, plugs, wires, modules, everything.

Ford parts from the counter are usually no more expensive than the parts store, and aftermarket Ford ignition parts rarely work.  Tight specs.  Get everything from Ford.  That's 7 years of auto repair shop experience talking.  After about one year of scratching my head buying all of my parts from O'reilly and the Zone, I never could get parts-store Ford ignition components to work right.  I hired a new tech who had been a Ford tech, and he turned me on to this little truth.

I thought, "crap, there goes my parts profit margin," but surprisingly, the prices weren't that different from the dealer.

And the delivery driver was really cute.  YDDMV

Dr. Hess said:

My methods to check spark plug wires:

Method 2:  (requires less tools).  With the motor running, grab each spark plug wire in turn with your bare hand.  If you get thrown across the garage at any point, that wire is shot.

Method 2 has me LMFAO. I have often thought about a funny YouTube channel that makes fun of these garage shows. Kinda like “This old box” from In Living Color. https://youtu.be/1BNgRpRuWGs

Curtis said:

With wires, I always test resistance.  If they all fall within spec, I'll reuse during a plug swap.  If I see carbon tracking, I'll use dielectric grease in the boot and I haven't had any troubles.

I used to believe this as well, until I was having a problem with a high speed miss in my turbo Miata. I replaced plug, ignitor, coils - no effect. The wires checked out fine on resistance, but finally on FM's advice, I threw a new set of NGK plug wires on it and viola! No more miss.

I will admit that most of my stuff is older American.  You could probably use some 12-gauge Romex for plug wires and just get a slight miss on my stuff.