She borrowed two five-gallon cans from Darryl and bought a five-gallon Kerosene can at Wal-Mart on 3rd Jun. So she had the capacity to carry fifteen gallons plus the car's gas tank.
I disagree, respectfully. The gas purchases on 6th Jun may not help but the ones on 3rd Jun certainly will. They add to the prosecution's premeditation claim, in that she bought enough gas to avoid leaving a credit card trail in Arizona.
And she obviously USED the gas cans to get through Arizona, if she had to REFILL them in Utah.