Two experiments tested the idea that the principle of resource conservation moderates and limits automaticity effects on effort mobilization. Effort-related cardiovascular response was assessed in cognitive tasks with different levels of task difficulty (Experiment 1) and success incentive (Experiment 2) during which participants were exposed to suboptimally presented action versus inaction primes. As expected, implicit activation of the action concept resulted in stronger effort-related cardiovascular response than activation of the inaction concept—but only when the task was feasible and success incentive was sufficiently high. Effects on task performance were compatible with those on effort. The findings indicate that the automaticity effect of action/inaction primes on effort mobilization is situated, sensitive to task context, and limited by extreme task difficulty and low incentive. The findings facilitate a theoretical integration of automaticity in effort mobilization with the principle of resource conservation.