The release stated: "Both engine manufacturers will use a uniform Sunoco E85R fuel in 2016, with the removal of an additive (HiTEC 6590) previously allowed for Chevrolet," and based on the wording, it appeared Chevy was given exclusive use of a fuel detergent.

Asked if preferential treatment was at play, and if Honda was not permitted to use the same additive for its 2.2-liter twin-turbo V6 engine, IndyCar VP of technology Will Phillips provided clarification to the situation.

"HiTEC 6590 and 6403 are fuel detergent additives that deliver no added level of horsepower or torque performance," he told. "Both Honda and Chevrolet were provided the opportunity to use one or both of these additives in 2015."