NIC,

I don't put any metal rings inside the oil "containment" when I change the Oil. I use the dipstick sucking device and have all of them left over. When I had my 1975 240D, I had a place for each of the washers though. One went on the bottom of the oil filter (that arrangement was thought of by an evil engineer - the unit was designed to make changing the filter a nightmare) under the bolt that went through the center of the filters and held everything together, one under the pan drain plug and one under the oil cooler drain plug. In the W123 models much of this got "fixed" in that it is much easier to change the filter, and I think the oil cooler drain was eliminated at some point. The washers you get are copper, and they fit under the various drain plugs you may or may not have on your car. I think you get a full compliment of washers to make the washer arrangement of the filter kit non-specific to a model year or chassis number series. Consequently you get washers you don't need. I save them and have about three pounds of copper washers in a couple of bags now. I do not believe any of them go inside the oil flow path. Hope this helps, Jim