Oil Level and the 'O' Ring

I have never been completely happy when reading the dip stick on the Duratec.  I always felt I had enough oil in there but the dip stick barely had any oil on and it always seemed to be a bit of a thin film of oil.

I read a while ago about removing the 'o' ring at the top of the dip stick and so decided to give it a go.  The idea is that the 'o' ring creates a good seal and so pushes the oil out of the dip stick tube thus giving a false reading.  So today I took a reading and the oil seemed to just be touching the minimum.  I took the 'o' ring off and suddenly the oil was just over maximum !!!

So I have drained some oil, taken 3 more reading to check I am in the middle of the min and max.  Interestingly, putting the 'o' ring back on gave me barely a drop of oil on the dip stick.

Duratec Dipstick picture from Caterham website.  

The 'o' ring is on the yellow plastic section at the top.