I think y'all misread what I wrote. I never said anything about extending the oil change interval, I said I have logged 10K miles on the Suburban using semi-synthetic and that I had worries which were gone at the first change.
In that 10K the Suburban has logged, it is now on it's fourth fill of semi-synthetic and the 560, after 4K is on it's second. I guess I didn't make that clear enough to begin with.
Still running at 3K per oil change on all my cars.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.