I did a 60k service inspection on a 93 EV Westy last week. Motor was a
2.5 L gas 5 cylinder.

Factory plugs (VW/Audi logo) were Champion (made in Belgium) dual
electrode items. Siemens black box for the ignition. Bosch distributor.
The plugs after 30k were worn past 2.0mm. I know because that is the
largest wire on my Bosch guage and it slipped through with a bit of
clearance. Stock gap is 0.9mm. Client complained of rough running and
poor gas milage. No wonder.

Up to this point I have advised that the reasonable maximum life on a
tight motor with the later high energy ignition is 20k. Combustion
efficientcy tends to drop shortly after that if it hasn't already.

Based upon this experience, I ain't upgrading my recommendations,
Particularly with the cost of gas these days.

Also, if you don't pull those plugs periodically they can get bound
up tight enough to damage the threads. Use anti-seize compound, you
say??? Some of those anti-seize compounds will loose the anti part
and become seize compounds, hard as hell and will insure threads on
the floor. I wonder how those 100,ooo mile between "tune-ups" Fords
are holding up.

At 62k, the only problems of note have been with the window lifts.
The mechanism had weaknesses. Two have been replaced on this one.
The last one was an updated design so that issue may have been
resolved. The only other failures have been the exterior rear view
mirror. The stepper motor ist nicht. The cooler (under the drivers
seat) is going bad. That's the second one i've seen.

It is amazing how fast this very heavy vehicle is. Ausgesehtnet.

Doktor Tim
Maintenance Repair and Restoration of European Vehicles
San Juan Island, WA