[sammyg2]

It might be normal but I'd think that after 10 minutes it would probably be gone. Was it really cold outside? If so the water vapor might be visible even if the engine is warmed up.

or it might be a head gasket or a cracked head or block.

if a head gasket was leaking into the radiator the radiator would pressure up over time and pop the relief on the cap and vent into the catch bottle and probably wouldn't show up as steam out the exhaust.

Steam out the exhaust after the engine and exhaust is warmed up could indicate that water was leaking into the combustion chamber (possibly in the intake tract).
In that case the static cooling system pressure test would show the pressure dropping off over time.
A compression test might show it but might not.

If water is getting into the combustion chamber, some of it would most likely get past the rings and into the oil changing it's appearance if it had time and ran long enough. 10 minutes probably wouldn't be long enough.