Good info. Yeah the normal RPM commuting drives on relatively flat roads don't seem to consume much, if any, oil.I have owned many subarus and about to get another. Starting way back with a 1990 Loyale thru many Impreza Wagons, a Justy, an SVX(!), various Foresters and now a base Outback.
The EJ and the FB 2.5 use oil and I think for different and varied reasons - some of them improperly drilled valve guide pilot holes(TSB), some ring and piston design(TSB) , and many just a healthy PCV scavenging on a crankcase design that puts the crank and rod bearing spillage close to the vacuum side of the PCV.
I would hazard a guess your usage is just PCV related - unless you have been seeing excessive consumption in regular commuting prior to these trips. The PCV are usually clean as a whistle if you regularly change your oil - so no use changing it.
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- 1987 Subaru Justy Brochure cover courtesy of Import Archive