this site says that 18/0 is ideal for dishwashers http://www.silversuperstore.com/stainless_steel_flatware/quality_differences.html
"Chromium gives a flatware pattern its rust-resistant qualities. It is the best available in consumer stainless steel flatware patterns. The presence of Nickel gives a flatware pattern a superior shine, which is intended to mimic new silver flatware. Nickel is very expensive, and is a major contributor to the price of flatware.
So, here's what the numbers mean:
18/8 flatware - 18% Chromium, 8% Nickel
18/10 flatware - 18% Chromium, 10% Nickel
18/0 flatware - 18% Chromium, no Nickel
13/0 flatware - 13% Chromium, no Nickel
Which one is better? Well, if you want flatware with a high polish finish and superior rust resistant qualities, pick a flatware that is 18/8 or 18/10. If you are opening a restaurant, and want to keep your costs down, as well as being able to wash it several times a day in the dishwasher, pick a 13/0 or 18/0 flatware pattern with a cheap, flat handle knife."