The oil dipstick tube is for sucking out crankcase oil and insertion of special measuring tool in the event of excess oil consumption. Like all recent Mercedes, my 06 ML500 also has the dipstick tube sans dipstick. Since I, like you, prefer the manual measurement method, I ordered a dipstick for the W163 ML500 thinking it would work. Alas, Mercedes has lengthened the dipstick tube on the W164 ML500 so the W163 dipstick is now too short and does not reach the oil level even when properly filled. Viagra might be in order. Mark