*All* long-time airplane drivers are fanatics!

Aircraft engines run in a nearly totally different environment than cars. A major difference is that they run at 75% power for hours at a time, and are certified for doing so at 100% power. Very few cars on the road will survive that without a lot of mods. Aircraft plugs are, as a consequence, relatively "cold" and foul easily on startup and at idle. They are the equivalent to "track" plugs.

Since most airplanes have variable a/f ratio controls (the 'mixture' ****), one has a chance to, and is indeed required to, play with it. It's quite amazing how much it can be varied with no misfiring at all. The most efficient cruising condition is considered to be a the peak EGT reading. However, there is considerable variation between cylinders, so one nudges the mixture control forward (richer) to give a 50-100 deg F drop to be on the safe side. Some guys put an EGT for each cylinder, to then one can run at near-peak EGT for the leanest cylinder. (However, going to full power with the mixture "leaned" may result in instant loss of $30,000 from one's bank account, plus an unplanned landing.) This, and what he's talking about in the article, would however be impossible to do on the street, unless you can find a perfectly flat highway to run 75% power at 120 mph for many minutes along.

As a practical matter, the change in plug resistance over time may be more important. A friend ran his Honda for ~100k miles on the same set of plugs. No misfires at all until $700 worth of ignition system components fried. The ignition circuits are designed to work with a specific plug electrical resistance, if that varies, it will fail in a way similar to hooking up an 8 ohm stereo amp to 2 ohm speakers.

At least $70/four plugs seems cheap to me. Good platinum airplane engine sparkplugs run $100 EACH; 2 plugs/cylinder x 4 cylinders = $800. Even stretching them to 200 hours gives $4/hour just for sparkplugs ....

One reason I don't have an airplane any longer.