[Rod Schneider]

Airplane engines do use a fair amount of oil, especially compared to most auto engines. The average Lycoming or Continental engine in a small plane shares two design similarities to the Porsche--they are horizontally opposed and they are air cooled. Air cooled engines experience a wider range of temperatures than a water cooled engine and are designed with wider clearances to compensate. That leads to higher oil consumption than in a similar sized water cooled engine. I don't think the cylinder layout has as much to do with it--I've got a Subaru flat six on my airplane, and others who use the same engine report little or no oil usage between oil changes.