I was curious. I always replace the rubber gasket. $1.99 from advance auto. Fel to is rubber brown $2.49. I use a pen too pry the old one off,and put new rubber one on like twice a year sometimes one,I do an oil change..3700-4000 miles by then.depends.
Last time I used a copper washer,from local hardware store was way back in 1995. I had a 1985 Isuzu I mark hatchback. Doing an oil change driveway that spring I used a copper washer on plug.no leaks at all! So thought maybe is it possible on the LeSabre? Like the pic listed in post..the copper ones,think they're work?