On a recent trip of a few hundred miles, my wife and I were traveling in
convoy: she following our van. On one occasion she saw a puff of blue
smoke come from the van's tail pipe an smelt the burnt oil. It happened
only once that she could tell. This happened well into the trip so the
engine was well up to temperature. It happened on a flat section of road
at about 60 mph. The van is running on Mobil 1 15W50.

Can anyone shed some light on how the oil got into the cylinder? Any way
that I can think of could not happen only once.
-Larry