The petroleum industry is the #1 tax paying industry to the federal government - something on the order of $50B a year IIRC. In that context, a few percent of that being returned in credits / tax breaks or outright subsidies is more like the 'Cash Back' feature on our credit cards
That's ignoring the indirect subsidies. For example, how much has the government spent on diplomatic, military, and economic pressure on the middle east to try to keep oil prices stable? How much was spent on subsidising the federal highway system, which promoted demand in petrol? How much was spent on the tax system that incentivised US car manufacturers to produce fuel-inefficient vehicles by treating SUVs as trucks and giving them a lower tax rate?