This dataset contains mobile measurements of ambient methane collected during a controlled release of methane. Methane was released from a stationary source while a vehicle repeatedly drove past the release point, transecting the resulting methane plume multiple times. The objective of the experiment was to evaluate the capability of mobile platforms to detect methane plumes and to examine the relationship between methane release rates (in L/min) and key plume metrics, such as the maximum measured mole fraction and the integrated methane enhancement during individual plume transects. The experiments were conducted in Toronto on October 20 and October 24, 2022.