Manny, there's actually a big difference between the two. Problem is as you noted is this 15k oil change idea is a bust.

Under no circustances should you drag around oil for 15k miles in an MB. You have GOT to get the dirt out of that motor, and the oil change is the only good way to do it short of dismanteling and physical cleanout.

On big sumps like the 12's and big 8's the oil will hold a good amount of dirt in solution - most of which has bypassed the filter. But it's got to come out of the motor sooner rather than later, IMHO somewhere around 4-5k miles.

Sludge, intake clogs, valve guide clogging, EGR clogging etc ALL have to do with natural dirt and combustion mess in the motor that can't get out.

True, the oil itself is remarkable and will not break down prior to 15k miles. But the dirt it carries around will wreak havoc with your motor, regardless of size, compression etc