As regulars here will know, I keep very close tabs on my oil consumption,
trying to make the observation as close to a science as possible.

My latest test period (ended today) reveals consumption of 2,150 miles per
US quart.

Thus far in my record keeping:
1,500 mi/qt at 295,417 miles;
1,800 mi/qt at 296,494 miles;
2,500 mi/qt from 296,919 to 297,919;
2,150 mi/qt from 298,032 to 299,184.

It's been roughly 1,500-2,000 mi/qt for a few years now, but lately I've
decided to keep much more exacting records in an attempt at determining
consumption more precisely, and for spotting any trends or correlations. I
decided to do this after experiencing a few apparent episodes of alarmingly
high oil usage the summer before last.

I have discovered there is a direct relationship between how hard I drive
and the oil consumption. The higher the revs, the greater the throttle
openings used, the higher the oil consumption. This is, it has been
explained to me, a sign of a well-worn engine.

As a contrast, our Toyota Tercel has 90,000 miles on it. Normally it uses
no discernible oil between 2,500 mile oil changes. Last summer we passed
through the hills of Pennsylvania, all the way across PA to VA and DC. That
little engine therefore spent much of its time at full-throttle and high
revs, attempting not to lose speed on very long upward grades on the
Interstates. During that entire trip, the car used something around 1/8 or
1/4 of a quart in something like 1,000 miles. It would appear that even
new-ish engines with good rings are still prone to higher oil usage under
extended heavy load.