If I switch to an OM606 powered MB Diesel, I'd never detect these noise related problems until they became really really bad
heheheh...
BTW, I just switched to Delvac One on my OM617. I honestly don't know what improvements I should be looking for. It runs just the same. Maybe less "numb" when it's cold that's all. (Previously my car was VERY VERY slow when it's cold)