Synthetic oils

I've run my last 4 cars on Castrol syntec and Elf synthetic , change oil and filter every 28,000 km or so and never burnt oil between changes, all cars had over 450,000 km on them when sold with zero engine problems . No oil used between changes , pans were clean , no sludge build up . Cars were 1977 ramcharger 440 over 400,000 miles , 90 T-bird S/C 190,000 KM (STOLEN) 1992 T-bird S/C 470,000 km , Ford Exploder 440,000 km , current Nissan pathfinder 120,000km and 2009 Jeep Sahara 60,000 km .
The 90 bird factory supercharger oil was spec'd to change every 60,000km , 92 bird had synthetic oil in supercharger that was spec'd for life of car .
Changing oil every 5,000 km is a waste of resources , have had the oil analyzed a few times at 28,000 km and they were still acceptable . The oil change schedule is there to MAKE MONEY and keep the dealer and corner garage busy , at leat that's my opinion .
And I beat the crap out of those cars .