Amazing vehicles for racking up miles. Thought of using synthetic oil? Have just converted my '83 240D (bought in Dec) to synthetic at 250k miles - noticable improvement in performance, less drag.

IP has no separate oil sump, routes off the engine instead. You can turn the engine using the power steering pump pulley for the valve adjust. And what I've done is discard the fan shroud to access the engine front. Your fuel mileage sounds typical to me, might get better with synth oil in the crankcase. But i cant vouche for mileage w/ AC, not working in my car. Changing the oil in the differential is good idea too. And think about flushing the coolant if you havent already, also flushing hydraulics with fresh DOT4 to extent the life of brake hoses, callipres and master cylinder.