No oil pressure would not show a thing, Yes I am LAME.
IT is oil mist drawn up from the filler port, yes at angle of attack that makes the mess - blow over a open bottle of red and it will whistle a very full bottle on a angle will spill blood.
At first sign close cowl flaps and slow as much as possible, lower nose, that is not in the book - but neither is opps with oil cap off.
It will be bad for engine but not fatal, maybe a top down the track.