While we're talking about adding oil it should be noted that you do
NOT add oil to the upper notch on the dipstick.  Half way between the
two notches seems to be the agreed "normal" level. Common experience
suggests that adding oil more than half way between the notches will
trigger the "Rear of vehicle automatic anti corrosion device". Or, in
other words, the "extra " oil will blow out and leave a nice film
over the rear hatch.      Fill to the half way point and NEVER fill
it above the upper notch.