I just had the first change done, free at the dealer, idiots. I told them the speed 3 takes 5W30 and they said they use 5W20 on the 3. I showed them in the book where it says 5W30 but they put in 5W20 anyway, said the tech checked with Mazda and it was okay, and in our climate it was better. I live in Phoenix and its already in the 100's here, wouldn't you go with a higher viscosity in extreme heat?
I think they did not have the Mobile 1 in 5W30. But they did Mobile 1 for free thinking I will go back to them.
Btw, I believe the 3K oil change only benefits those selling it and is a waste of money. The book states 7.5 K in normal conditions and 5K for heavy conditions. So running Synthetic for 5 7k should be very safe. The nice thing about synthetic is if you go past where you should, you have a little extra protection.
My .02 on oil, a fascinating subject by the way.