Just did a spark plug change at 227,000 miles. The car has been taken good care of, and looks like a grandpa's cream puff, which it is. At idle you can balance a teacup on the valve cover, it's so smooth.

Number 1 thru 3 plugs looked fine, but #4 was harder to get out; it had some minor rust on the threads; but none on the section of thread that goes into the engine, All four plug tips looked tan and worn, just like you'd expect after 30K.

All four piston tops looked like what you think a high mileage engine would look like, carboned up a bit but not too bad. There is no water in the oil or vice versa.

Also noticed that the oil seal at the bottom of #4 was seeping a bitl; the idiots who replaced the valve cover gasket didn't replace the seals at the bottom of the plug access shaft where it meets the head,.

Additional info: I drove the car very little this last year, and put off the oil change until it was about 3-4K on the oil over that year, Should have replaced the oil and filter at 6 months, regardless. As a result, the oil has broken down, and it's really using it as compared to before-nearly 1/2 quart in 500 miles.) (Going in for a change next week.) Hope this didn't screw the pooch. Also, got caught in an hour-long traffic jam a few weeks ago on the freeway on that old, bad oil. Could that have caused it to use more than normal? (No one dared turn their motor off, SWAT situation.) In the past, the car has used very little oil except towards the end of 5000 miles, when I change it.

Question:

Could I have a slight crack in the head at the threads of #4 spark plug, or can an slight oil seep attract moisture down into the thread, and just cause a bit of binding and corrosion?

Car is high mileage 227,000. Specs:

2001 Protege LX 4-door, loaded.2000cc, auto air, everything.

Thanks to all in advance!