1996 c180 and lots of blue smoke

[S34n]

I have a 1996 c180 auto with 107k miles that's chucking out lots of blue smoke at random times. It's mainly after about 20 minutes cruising at motorway speeds or after a bit of spirited driving it poors loads out if you come of the throttle and go back on it, eg coming up to a junction, slowing down but being able to carry on without stopping. It fills the junction with blue smoke! But it's only on the letting off/back on the throttle.
I just took the plastic air intake off and found a lot of oil in there from the crank breather pipe, cleaned it out and it seems fine again at lower speeds. Any ideas?

[bolide]

Blue (oil) smoke on the overrun is normally caused by worn valve guide oil seals

Nick Froome