genericTerry t1_j1fnrru wrote on December 23, 2022 at 11:45 PM

Reply to comment by marengnr in How does the non-CO2 emissions of an external combustion engine compare to an internal combustion engine? by Past_Self_4845

Excess oxygen is also $$$ going up the stack as your heating up air as well as the combustion products.

paulHarkonen t1_j1hxkvz wrote on December 24, 2022 at 2:26 PM

Not to anywhere close to the same degree. Excess fuel consumption is way more costly than heating up a little bit of extra air.

Obviously you want to run as close to stoichiometric as possible, but since we are only human, running a bit lean is less expensive than running a bit rich (all other factors being equal).