Modern plug gaps are wide, so these coils work hard from mile 1. As good as these
modern plugs are, they will erode a bit during their rated life - so by end-of-rated-life of these plugs, these COP coils are
working pretty hard.
Its amazing what a difference a new set of plugs and wires makes... We recently replaced the plugs and wires on our '97 Dodge 1500 and the next tank went from 9mpg to 11mpg for the first time in the 7 years I have been around it.Plug wires, OTOH, are pretty rare these days, and those DO get faulty after a lot of miles and years.
That is why I monitor the gaps on my Iriduim plugs on my MR2. They were still nuts-on at 80K miles. I have never
had a coil-on-plug go bad on a Toyota I have owned or worked on (many). I have replaced the coil "cassette" on
a friend's Saab 9-5 Turbo. On that terrible model, you can only replace the 4 coils as a set, even if only one is bad.
Plug wires, OTOH, are pretty rare these days, and those DO get faulty after a lot of miles and years. Subaru was
one of the last major brand holdouts with a distributor (gone now). Any other new vehicles with a disti? My
own 04 Tacoma shares 3 coils with 6 cylinders, so it has HT wires, but no disti. The older Lexus V8s (similar to
Tundras maybe?) have a disti and very hard-to-access plug wires buried under panels and brackets. 10 y is
all you get out of those.
Its amazing what a difference a new set of plugs and wires makes... We recently replaced the plugs and wires on our '97 Dodge 1500 and the next tank went from 9mpg to 11mpg for the first time in the 7 years I have been around it.
Aaron Z