Mobil 1, good for 6k miles?

[73 Mustang Boy]

I run mobil 1 in my car and like it alot. I change my oil every 3000 miles like everyone says. Synthetic oil probably will last 12000 miles like mentioned above but the filter is only good for about 3000. I would run synthetic oil in any car that is driven daily because it breaks down at a much highter temp than conventional oil. If something happens and your car overheats synthetic oil will protect the engine much better than conventional oil. Thats my 2 cents on the subject.