Would I go 15,000 miles between oil changes ? No way . I am an old redneck . Accustomed to 3,000 oil / filter change interval .
On our 2015 Chevy Sonic 1.8l automatic , I watch the oil life % . I change the oil / filter at about 50% , but do not reset the indicator . Then change oil / filter at about 5% . Then reset the % display .
We got 4 free oil changes in the first 24,000 miles from GM . I guess they used GM Dexos , which is a synthetic blend . In between , I have used either Mobil Super Synthetic or Mobil 1 ( regular ) . Both Dexos spec .
If I start using the EP Mobil 1 , it would be on the hope it is better than the " regular " Mobil 1 , for roughly the same money , at Walmart . But I would continue to change oil / filter at 50% & 5% .
Roughly twice as often as GM requires .
BTW , GM keeps track of oil / filter changes via OnStar . I suspect if you do not follow GM's guide line , it might void the warranty ?
God bless
Wyr