Cruz being from Texas is mobbed up with big oil and that is why he's against renewable fuels such as ethanol. Most gasoline today is 10% ethanol and the biggest producer of ethanol is Iowa. If Cruz gets his way and eliminates the Renewable Fuel Standard it will not only raise the price of gasoline for all Americans but it will devastate Iowa's economy.
Many lying conservative groups have criticized the RFS as crony capitalism, also noting that it has failed to be the promised panacea to America’s dependence on foreign oil or reduce greenhouse gas emissions, plus the problematic corrosive effects that ethanol-blended gasoline can have on engines in automobiles and power tools.
The US is becoming energy independent and Iowa's ethanol production has been part of the solution. As to the claim that gasoline blended with destroys engines is total and complete bullshit.
Cruz is inarguably the most high-profile opponent of the Renewable Fuel Standard, otherwise known as the ethanol mandate—a pro-ethanol regulatory subsidy—within the GOP primary field.