California’s war on carbon could blow back at the pump — and wipe out the state’s oil business entirely, a top Chevron executive is warning.Andy Walz, who heads the company’s downstream, midstream and chemicals division, says a looming vote by the California Air Resources Board could pile billions in new costs onto in-state fuel producers — potentially driving refineries out of California for good.“If they add this burden … it’s not whether refineries will close, it’s when,” Walz told KCRA