Normal maintenance.
Oldest & most used Wrecker I have. 410,000 miles on original engine. Had 3 clutches & 1 transmission rebuild (5-speed). Still has reasonable pulling power. Burns 1 quart of oil every 700 miles on the highway. Burns 2 quarts of oil idling overnight for 10 hours.
With respect to the amount of oil any diesel engine burns while at idle overnight, or for any prolonged period of time... the consumption will almost definitely be reduced if the idle speed is raised to something on the order of 1100-1300 r.p.m., rather than the normal 700-800 r.p.m. The lower idle speed leads to much quicker degradation of the oil than will happen at the higher speed. Also your fuel consumption will not be noticeably affected, due to the very high air to fuel ratio of the injection pump at these engine speeds.
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