Lots of possibilities! Worst case is a leaking injection pump,
requiring rebuild, but that won't be 3% very long.... more like 50%.
Unless you are "making" oil (level rises on dipstick!), not a worry.
There is always some unburned fuel that gets into the crankcase when
you start a cold engine, and if it runs rough there will be more
(longer running with poor combustion and extra fuel injected). Ditto
for any other condition that allows or causes poor combustion (low
compression, late injection and/or valve timing, poor nozzle condition,
etc). Not getting the engine fully warmed up and the oil hot will also
allow it to accumulate. You will also have high water content under
those conditions.
If it's within specs, see what it is next time. If it goes up, time to
search, if not, it's fine.
Peter
