Oil cap air

[varix]

This is probably a stupid question, but... Recently I removed my oil cap with the engine running and noticed a lot of air blowing out the hole. It feels like its blowing out as each piston moves up and down. Is this normal? From my understanding blow by is when the combustion passes into the bottom end of the engine so it is unlikely to be that... If it is normal, what is causing this air?

[sergei]

No smoke?
if so that is fine, when piston moves down it displaces the air inside the engine (crank case side) when air is pushed out through oil hole it tends to go in a narrow stream, when piston moves up it suck air from outside though oil hole, when air it is sucked it is sucked evenly from all sides, hence you feel it only blowing (same applies for subwoofer port - it feels that it blows air constantly but infact the amount of air inside is constant in longer term).

[varix]

Car is using oil, probably goes through all the oil in about 3-5000ks. It doesnt blow smoke at idle, and blows some at full throttle. Slightly bluey black, (probably rich + some oil burn). Doesn't leak any. Normal for an old 4AGE?