Gentlemen, I conceed without reserve that oil and engine build tolerances have improved over the years. When the E34 eas built I guess it would run 10-40 or 20-50 depending on climatic conditions. I don't belive that thinner oil in a worn engine is a good idea. Oil is alkaline at manufacture to counter the above mentioned acids from combustion. More of those acids will get to the oil in a worn engine.
Oil contains a sacrificial element to counter the wear at start up. There is only a finite amount of those compounds in the oil. Again they will be under greater demand in a worn engine environment.
I would like to know if any restriction is placed on older or big mileage engines by Mobil? In any case My MINI's go 12k kms between the changes - book is 25. My E38 goes 10k - book is 20k. My e30 and E23 go about 8k kms between changes - much older engines 350k kms on each vehicle. Maybe I'm fussy but my vehicles are expected to last MORE than my life without curbed wheels or slammed doors.
I don't see leaving the oil for 4 years in my E38 garage queen as a good idea. I woulld like to know what time span Mobil put on their oil rather than the distance. I doubt it is more than 1 year so even THEY may suggest an oil change for me at only 6k miles. I would also suggest that my father's 1959 Morris has survived because of over frequent servicing, rather than inspite of it.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 White and 1 Light Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i
Last edited by BMWFatherFigure; 10-07-2012 at 02:22 AM.