What I find funny about rocket engines is that their effectiveness is uniquely based on how fast exhaust particles leaves the nozzle. Other types of engines like car engines don't do this, and only the rocket equation cares about exhaust speed.
So for example, oxygen/hydrogen engines will literally run at a worse ratio of 6:1 instead of 8:1 because the stray hydrogen atoms leaving the nozzle (due to there being less oxidizer to compensate for the hydrogen, and so some escape) decrease the average atomic mass of the exhaust particles since hydrogen has a way lower atomic mass than H2O molecules (the product of the reaction of combusting hydrogen and oxygen) do. They are literally designed to be less efficient in fuel ratio and yet are more efficient in speed because of that
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