Copper washers can be reused if you heat them red hot and let them cool in air. This softens the copper. I have been doing this for years. As a matter of fact, I changed the oil in my Porsche yesterday. It was the 5th time the copper oil plug gasket was reused. No leaks occurred.

Matter of fact, I replaced the fuel filter on my 400E about a month ago and reused those washers - they were copper. There was/is no leakage.

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Lawrence Coppari

2002 SLK32 AMG
2005 Acura TL
1987 328GTS
1986 944T