You mean Mobil 1 20W-50 is petroleum-based vs Synthetic? if that is the case, then yes I am using the petroleum based. Actually the MB dealer did the last oil change.

The dealer recommends changing oil in 6 months or 7000 miles and I want to change it at 3500 intervals. Do you recommend changing oil filter after 3500 miles or wait until the 7000 miles?