Yeah I noticed the hole through the tin wear. I had a pancake filter on mine for a while, what I did was cut a piece of metal to cover the hole in the tin wear. Bolted it on. Jobs a good un!
As a temporary measure, you could take 2 jam jar lids, drill a hole through them, then nut and bolt them either side of the hole to seal it up until you get the original filter in place.
I've a similar problem with my TP 1600 engine- but as the advice is always for 2.5l i make sure I add that amount and have always assumed that something funny happens with the dip stick - I'll leave it a while in future before reading - the stick is a relatively tight fit so I guess the air coudl displace the oil temporarily.
I put 2.5 litres into my AS engine and it comes up to the higher mark. I read somewhere that the lower mark represents "half full".
Im not convinced that the dipstick ever displaces the oil to the degree that it'd effect the reading... Just keep it between the 2 marks and happy days.
I have a similar issue with my vega 2.0L................put 3.5L in after oil and filter change....need to top up with extra oil to reach top mark of dipstick, so about 3.75L Have always filled to top mark and done 3+ years and about 10k miles with no ill effects.
