  With in the extended thermodynamics, we give a comparative study of critical
heat engines for Gauss-Bonnet and charged black holes in AdS in five
dimensions, in the limit of large Gauss-Bonnet parameter $\alpha$ and charge
$q$, respectively. We show that the approach of efficiency of heat engines to
Carnot limit in Gauss-Bonnet black holes is higher(lower) than charged black
holes when corresponding parameters are small(large).
