The FSS interval starts out at 10,000 and will adjust according to all the variables it monitors. In your case it will come on at the one year mark after you got the car.
Your dealer will change oil and filter at no cost during the warranty period at the FSS interval. There was a post by a pro tech a few weeks ago that indicated they had seen some sludge in some engines that had oil changes at FSS intervals. He said he was not supposed to talk about it, but it was easy to read between the lines.
John, oil is the cheapest insurance you can dream of for long engine life. I am using Mobil One in my new M112 motor and changing it between dealer recommended intervals.
If you pay for it, they will change it for you between FSS intervals. If you still want to go the full distance, I recommend using Mobil One to give the engine a fighting chance. I use Mobil One in my new engine anyway, and still change it at about 5,000 miles.
Also, if you only drive 7,500 miles a year, you should change it on a time basis not mileage. The FSS will let you go one year before telling you to change it regardless of mileage. Don't go one year, change it every six months.
If you were to change oil every six months with Mobil One, it would be about $30 worth of oil and a $7 filter. Is your car worth spending less than fifty bucks every six months? With such low annual mileage, changing your oil every six months and using Mobil One, I would be willing to make a very serious wager that you will get rid of the car because you're tired of it, or you decide to give it to your great grandson, before the engine would die.
Best of luck, and enjoy,
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in