Which would be a better oil to use Mobil 1 extended performance or Valvoline synpower?

Every new car in America that comes from the factory with full synthetic oil in the crankcase is Mobil1. Chevrolet Corvette and Dodge Viper to name two. All GM cars and trucks built after 2011 came from the factory with Dexos1 if it was gasoline powered and Dexos 2 if dad a Duramax Diesel. Dexos 1&2 as purchased from a GM dealer is a semi-synthetic made by Rotella.

Valvoline dragged their tail and at fist said it was too expensive to even test their oil to see if it passed Dexos licensing. GM will not warranty an engine failure with a goofy "compliant" rating. There is no difference between Valvoline full synthetic and Mobil1 cost at Walmart. Mobil1 Dexos licenced is less expensive than semi-synthetic Dexos at a GM Dealer parts counter.

There you have it! There should be no question in your mind what the best oil is with no warranty gripes down the road.

Mobil 1 Dexos

Either one is just as good