Even though I feel synthetic oil is overkill for most water cooled applications, with 3500 mile change intervals, I am a long time user. I also push it to anyone who asks advice on the subject. However, if using Mobil 1 it is recommeded that the change intervals stay about the same as with Dino based oils and this varies greatly from car to car.
Below is an excerpt from the Mobil1 site.
BTW: ran into a friend yesterday who mentioned that his wife brought her MB MLxxx to the dealer for an oil change. Said it cost $450....three filters etc. Is this the going rate?
Oh, yes he mentioned that he received a $35 rebate coupon from Mercedes but it wasn't honored. Hmmmm
Myth: You don't have to change the oil as often when using Mobil 1.
Answer: While Mobil 1 has given excellent results in extended oil drain tests, ExxonMobil prefers to remain conservative with oil drain recommendations. ExxonMobil engineers recommend that you can go all the way to the maximum mileage or time frame shown in your owner's manual for oil changes when using Mobil 1 with SuperSyn™. This allows the reserve protection capabilities of Mobil 1 with SuperSyn™ to cover unusual or unexpected driving conditions.
Oil change intervals can be as short as 3,000 miles or as long as 15,000 miles on some new cars. Mobil 1 with SuperSyn™'s high-performance reserves can give you the confidence to go the full mileage or time frame recommended by the vehicle manufacturer. Mobil 1 with SuperSyn™ is especially suitable for the latest vehicles with extended drain intervals or vehicles with oil monitoring systems that vary oil drain intervals.
'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac