With the industry spending billions of dollars to meet tougher emissions and fuel economy rules, Christopher Grundler's office has been on a mission to keep the playing field level.

Since the end of last year, audits by the EPA's emissions lab in Ann Arbor have led Mini and Mercedes-Benz to revise fuel economy labels. Ford also revised the mpg stickers of several models this summer after internal audits - which the EPA has encouraged all automakers to do - found inconsistencies between production and prototype mpg data.

Last month, announced Nov. 3 the EPA and Department of Justice hit Hyundai and Kia with a $100 million civil penalty for systemic" testing errors that led to widespread bogus fuel economy numbers at both brands in 2012. The fine was part of a broader settlement that included more than $200 million in forfeited greenhouse gas emissions credits used to track compliance with the EPA's tailpipe emissions program. The companies also must establish new fuel economy testing and certification operations