. . . and 5W-20 for 2.3 non turbos.The 2008 Mazda3 manual says to use 5w-30 if your car has a turbocharger.. or in otherwords - if you have the Mazdaspeed3.
If 5W-30 is good enough for a turbo, than it's got to be OK for a non turbo ?
Besides the 5W-30 is usually easier to come by.