Is there a recommended time or mileage interval to change out the spark plug wires on the '01/2.5L ..I am familiar with the various "resistence" tests that one can do and the "glow" in the night approach with a fine mist water bottle sprayer, but sometimes that does not tell the whole story...what about unseen current leakage through the wires covering??..I ask this because every so often my mothers mini van has the plug wires changed out because one or two of the wires have turned very dark in color indicating current leakage (according to her mechanic) as compared to having a very lite color when newly installed...

Depends on the plug. Copper plugs, I'd do every 30k or so. Platinum plugs are supposed to be able to go to 100k, however I'd probably change them sooner.....that's just me.

the short answer, your owners manual will give you vehicle/model specific information.

the long answer: that it happens on one vehicle, doesn't mean it happens on all. you will not see this kind of activity on your subaru. certain vehicles burn through wires at an excessive rate, not so with subaru's. the most likely way for subaru wires to degrade is by someone removing and reinstalling improperly or tearing/damaging the end. your owners manual will tell you how often you should replace them. 60,000 miles is a healthy time to change them assuming you have Subaru OEM wires, but they can easily outlast that if you like doing it that way. you should always use OEM wires on this engine. the EJ series engine (like your vehicle) are not good candidates for anything but OEM wires. the only other suitable alternative is magnecor. i always use magnecor spark plug wires and never replace them again, they will last the life of the vehicle and will not break-down. they are excellent, check out their website, they are a no gimmicks high quality manufacturer. no other aftermarket wire should be used on this engine. i also use magnecors on all other vehicles that have incessant wire issues like the minivan you mentioned. it solves the problem every time forever.

I usually wait for a reason. Wires made today can go 50 -100K miles without any problem. The first sign that its time is some ignition noise in the radio, or a slightly rough idle in the morning. If I'm replacing plugs, I replace wires. I dont go by soobies intervals for plugs as they seem to be too short.

 

nipper

Replace when they break.

 

Broken cables give a very characteristic rough idle.

I just did my 99 at about 100 thousand. The factory wires are very high quality and seem to go that far no problem. If you replace at or about that interval, they will probably last the balance of the life of the car for most people. I had a slight hesitation problem which was helped to an extent by replacing the wires.

127,000 miles and still good.