The objective of this study is to investigate the interfirm comparability of climate performance disclosed in the sustainability reports produced by car manufacturers that have been criticized over the past few years. The in-depth content analysis of the data disclosed by 17 car manufacturers over the period of 2014 to 2017, covering the five main climate indicators from the Global Reporting Initiative standard, shows that it is impossible to make meaningful comparisons between companies' performance, regardless of the intrinsic reliability of the data disclosed. A detailed examination of the data obtained highlights the four main difficulties that prevent a rigorous and credible ranking of the climate performance disclosed in the sustainability reports: the fuzzy and eclectic measurement methods employed, the unclear and heterogeneous scope of measurement, the noncompliance and lack of standardization of the reported data, and the inconsistencies in and inappropriate contextualization of disclosed information. The use of three complementary theoretical lensesfunctionalist, critical, and postmodern-allows for a better understanding of the reasons underlying these problems. Contributions to the literature are set out, particularly on the measurability and comparability of sustainability performance. The practical implications of the study and avenues for future research are also explained.