Aging Plug Wires

99 Lexus ES, 120k. Would you replace plug wires just based on age?
Son leaving town, he is car clueless.

No I would not. I used a set of factory plug wires on an 86 Toyota Tercel for 20+ years and 300k miles, no problems.

yah…not as a stand alone job…unless there are currently runnig issues related to that…just add it to the next tune up.

Depends on how long he’s leaving town for. If you’re not going to see him for several years, and you feel like “just making sure” that they won’t wear out in 20,000 miles and leave him with an underperforming engine, then sure, swap 'em. It’s not like it’s all that expensive.

Otherwise, if he’ll be coming home for visits then you can do it whenever it needs doing.

They’re 17 year old rubber and can also be affected by the age and condition of the spark plugs.
What would I do if it were my car or a car belonging to one of my kids who was leaving town?

Change the wires and plugs. It’s a cheap investment in performance and peace of mind.

There’s different types and qualities of materials used in spark plug wires. The wires in my truck need to be replaced more frequently than the wires in my Corolla. hmmm … This is a Lexus, right? And the original Toyota wires? If so, what I’d do is clean them off with a cloth and little soap and water then take a careful look at them in good light. If you don’t see any obvious cracking of the insulation when you twist them, I’d leave them alone.

Toyota and Lexus spark plug wires use a carbon impregnated kevlar conductor, rubber insulation and a silicone rubber shield. They work fine and last a long time. Use a little silicone dielectric grease around the boots.

The boots will be the first to go, if you don’t see any cracks there, the wires will be fine.

I was actually thinking of a different kind of aging effect other than cracks in the insulation. I had a 98 Tahoe which began to miss just a little at idle, and if I went thru a carwash or drove in heavy rain it became much worse. Apparently the insulation had begun to break down or something and electricity was arcing to the valve cover etc upon occasion. In this case the plug wires looked just fine. Replacing them stopped the problem.

Wires are good until they aren’t, I would leave them alone until they ask to be replaced. You would be surprised at how long OEM Toyota wires can last. There will be ample evidence when the wires start to go bad.


I’m with OK4450 on this. But do NOT try to save a few bucks on the plugs and wires. Use only NGK or Nippon Denso plugs and OEM replacement wires from Toyota. Toyotas don’t like cheap parts. It’s an investment in your son’s safety (you wouldn’t want him breaking down in a high crime neighborhood), your peace of mind, and the longevity of the car.