I've used the same copper washer at least a dozen times in the past with no leakage.

It's a good idea to use a copper washer, and it's no big deal to change it every time since you get one with the filter.

Good luck,

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Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles