I get a 5qt jug of Mobile 1 from Walmart for $24.99 and pour 4 quarts in. So every 4 changes i dont have a to buy oil. I get mazda filters for free to cause my g/f's bro works at my local mazda dealer.
Mine's never taken more than 3.3 to put it to the full mark, even with a filter change. I've heard though it's ok (or even recommended) to run the MSP just a bit over the full mark.
I use 4 quarts of royal purple 5w30 and its a lil bit over the full mark but after a month or so it drops a lil bit below that so it wont hurt it to over fill it just a lil bit.