NOVELTY - The optimization method involves repeatedly applying first-pass D/Deff profile to computational model of fuel cell, calculating first-pass variable profile, comparing first-pass variable profile with desired range of variable, refining first-pass effective mass transport resistance profile or first-pass D/Deff profile if first-pass variable is not within desired range, determining second-pass variable profiles with second-pass D/Deff profile, and comparing relative performance of fuel cell with second-pass and first-pass variable profiles until fuel cell has superior cell performance.    USE - Optimization method for fuel cell diffusion media with spatially varying mass transport resistance. Can be used in electric vehicles and other applications.    ADVANTAGE - Selects diffusion media with spatially varying diffusion resistance, optimizes fuel cell operating conditions for a desired automotive drive cycle, and improves fuel cell performance and durability. Enables a fuel cell operation with acceptable performance and uniform relative humidity (RH) and current distribution (CD) along a length of the fuel cell. Ensures uniform membrane swelling that leads to a reduction in internal stress on the membrane, thereby resulting in enhanced fuel cell durability. Ensures that potentially damaging local conditions resulting from the accumulation of liquid water in the diffusion media or flow field channels can be avoided because the hydration state is much more uniform over the active fuel cell area. Ensures that the use of diffusion media with distributed mass transport resistance optimizes fuel cell reliability. Provides diffusion media that allows for reduced external humidification by optimizing the use of product water in the fuel cell. Ensures optimized use of water in the fuel cell further militates against the formation of liquid water in the fuel cell, thereby further improving freeze performance and durability of the fuel cell.    DETAILED DESCRIPTION - The effective D/Deff profile for the fuel cell diffusion media is provided if the fuel cell having second-pass variable profile has superior fuel cell performance. The first-pass D/Deff profile is provided for the fuel cell diffusion media after determining the baseline variable profile for the fuel cell. The baseline variable profile is determined after identifying the operating conditions of the fuel cell used in a vehicle, fuel cell variable correlated to fuel cell performance, and desired range of fuel cell variable. The first-pass D/Deff profile is refined if the performance of the fuel cell with the second-pass variable profile is less desirable than the performance of the fuel cell with the first-pass variable profile.    DESCRIPTION OF DRAWING(S) - The drawing is a flow-diagram depicting an illustrative sequence of steps for determining an optimum D/Deff profile of a diffusion media for a set of automotive operating conditions.    Condition, variable and range identification process (202)    Baseline variable profile determination process (204)    First-pass D/Deff profile provision process (206)    First-pass variable profile and desired range comparison process (210)    First-pass D/Deff profile refining process (212)