As referenced, the correct oil for a 99 E320 is one that is on the MB 229.5 list. The most common one to find is Mobil 1 Synthetic 0W-40. In order to take advantage of the FSS or FSS Plus (Flexible Service System) extended service cycle (10K+ or 1 yr) built into the electronics of your car you need to use a 'special' fleece media filter as well. Using a paper media filter and/or other non 229.5 synthetic oils with FSS can result in sludge formation as it did in early MY98 before people knew better.