Oil sump washer replacement problem

[in the making]

Hi,

I've just changed the oil for the first time on an NA6. There was no sump plug washer, so I put one on. Problem is I used a rubber O ring. Just read that it should be on of these. http://www.mx5parts.co.uk/sump-plug-washer-p-1087.html

Should I leave it or change it?

[pezchops]

do not use an o-ring for a sump plug washer.
o-rings are designed to be contained in a groove.
its not if it will fail, but when it will fail.
with heat from the motor and pressure from the sump plug the ring will fail.
i wouldn't drive that car anywhere like that if i where you

[in the making]

Thanks. Of course you're right.

I knew as soon as I was done it was wrong.