Is my engine allergic to oil?

[Tysoe]

Prepping for a trip down to Newquay last night so checked the oil and was low on the dipstick (below the bottom line) so i added about a pint which bought it to about half way between the 2 lines. Didn't test it last night but this morning engine is now reluctant to start, won't idle and power is on/off. Took it for a drive this morning and seems better when revs are high but struggles when low and oil light comes on when revs are low. Light comes on and goes off when cranking and won't start after a run.

Is my dipstick wrong which has led me to overfill it?
Engine is a 2.0 CU. Was running fine and idling well before.

Considering dropping the oil and filling with correct amount.

[Tysoe]

Well I dropped about a pint out and i'm in Bath! Dipstick is showing just under the first mark again.

Van running well and idling now but my oil light comes on at low revs/idle. Reluctant to put any more in but don't want to ignor the light!

[BOXY]

How long is the dipstick? Mine measures 22 .1/2" from the tip to the edge of the plastic stop at the other end. (not the thinner piece that fits into the tube, the piece that hits the neck of the tube.)

I run with my oil on the top mark without the engine slowing down. I've run it 5-10mm over a few times as well without any problems.

I doubt the oil level is the cause of the rough running.

[Tysoe]

I'll measure when I'm back from the beach

In convinced it's the oil level causing the problems > add oil = runs like bag of spanners, drain some oil = runs fine.

Will be interesting finding the cause!