Oxygen sensors means the car can burn the E85. The amounts of fuel going in are out of spec from the gasoline fuel maps in the ECU, so the check engine light will come on. The injectors likely can't allow the full flow of E85 required at high engine loads. In addition to the long term potential harm to rubbers and plastics, the alcohol, more likely the water with it, can damage steel parts. The 2000 flex-fuel Ranger had larger injectors and stainless steel fuel system, in addition to ethanol compatible plastics, in comparison to the non-flex-fuel model.