I posted a list of typical 3.0L CRD oil leak locations in this thread...
Here are the top 3.0L CRD oil leak locations in order of how often they happen!
1) Air intake tube in front of the turbo. Usually this is a steady drip of oil that eventually makes it way to the bottom of the engine. This issue generally happens on every 3.0L CRD eventually.
2) your oil fill cap was backwards, it leaks if installed backwards. Usually this is a stream of oil versus a drip. Just clean the mess up and reinstall the oil cap properly. This is common after an oil change at a location that does not often service the 3.0L CRD.
3) a third party oil filter - there are known problems with seals on some third party filters (Mann or Wix, can't recall which one had the problem). Generally this releases a fair stream of oil and is visible from the oil filter housing. Just clean the mess up and replace the oil filter with a genuine Mopar or Mercedes part.
4) a leak in your oil cooler - the oil cooler is near impossible to see to confirm this as the location of the leak. It is hidden under the top of the engine components. I will post up a picture if I can find one. The whole top end of the engine has to be taken apart, expensive and time consuming to diagnose and repair. This issue is rarely the problem, but has happened to 2 owners that I'm aware of.
5) a leak in one of the engine block oil galley plugs, here is a thread that shows them http://sprinter-source.com/forum/showthread.php?t=11326
Some galley plugs are near impossible to easily find, usually this will be a drip versus a stream of oil. An inspection scope helps to locate this one. Time consuming, but not overly expensive from a parts perspective to repair. This issue is rarely the problem, but has happened to 1 owner that I'm aware of.
6) Rear main seal. To confirm this, there is a black rubber plug on the bottom of the transmission bell housing, you can pop it off and access the flywheel. But the black rubber plug also gives some access to checking for a rear main seal leak. This starts as a drip and develops into a stream of oil. This is an expensive repair from a labor perspective because the transmission has to be removed. This issue is rarely the problem but has happened at least once that I'm aware of.
7) your crankcase breather valve or crankcase breather hose are plugged, usually the dipstick will blow out if this happens, however, according to what I've read, this can cause a rear main seal failure. Remove the crankcase breather hose and check for an obstruction. This is a more rare problem versus the others I've identified.
8) Turbo manifold seal. More likely this would've clogged before it failed. Lack of lubrication to the turbo will cause it to fail. This starts as a drip and develops into a stream of oil. This issue is rarely the problem, I've not read about a 3.0L CRD owner with this problem but arguably it could happen.
As you can see, many leaks start as a "drip" and work there way up to a more steady leak. You need to watch for the telltale drips and have them checked before they turn into a stream. By the time a leak is a stream, it can be more expensive and costly to repair.