I had to kill mine to remove it, i got a new one. new one came with a rubber O ring. old one had a metal washer.
what should it have had?
i did plug and filter up to recommended torque but have just noticed i have a leak

Old style plugs used to be plug and copper washer.

Later types were plug and Dowty Washer

Dowty washers are most commonly used in high pressure hydraulic systems and are essentially a steel washer with integral rubber oil sealing ring.

I have not seen the plug and rubber 'O' Ring (unless you mean Dowty washer) you refer to.

nope just an O ring.

dave said:

nope just an O ring.

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If the plug is the same then I'd be tempted to aneal the old copper washer and re-use.

Where did you get the plug from Dave? Fiat dealer. Also what part number.

I've never heard / seen of what you are describing.

For such a plug to work with an 'O' ring then the plug flange would have to to have a machined groove/recess otherwise the 'O' ring would be crushed and torn and never seal properly.

got it from http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=170501523616&ssPageName=STRK:MEWNX:IT

haynes manual for vectra says o ring, the washer that was on the old one wasnt copper

had a closer inspection of the old washer and it is a Dowty, but there is only a small amount of the rubber left on it i put oem expensive oil in too, hope i can change it with out losing too much

went to vauxhall dealers got new washer for £1, didn't need no vin numbers or nothing
now just got to try and get plug out an in without oil all coming out

dave said:

went to vauxhall dealers got new washer for £1, didn't need no vin numbers or nothing
now just got to try and get plug out an in without oil all coming out

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You'll have to tell us the technique! Presumably you'll lose some and get messy. Bad luck with the washer though - I wouldn't have noticed the difference.

got very messy, its a hollow plug with side holes so you can drain it easier, but it makes trying to get it in an out with out losing any a pain.

Hope you caught the new/cleanish oil in a nice grit free container. Put back in the top