I am wondering if there have been studies or calculations of the NOx emissions per mile of high MPG lean-burn gas-powered cars versus standard gas-powered cars.

Honda made some great lean-burn cars in the early to mid nineties. But the lean-burn era was short lived because the emissions were claimed to be higher.

However I am not convinced that the NOx emissions per mile is higher. I am wondering what comparisons have been made if any.

CO2 emissions per mile is available but I have not found NOx per mile.

My understanding is that concern about NOx emissions is the main reason lean-burn tech was not used more often.

Here is the link to one of the cars I am referring to. The gov site does not show NOx per mile, only GHG per mile and CO2 per mile.


  • 2
    Why are you not convinced? Lean-burn is similar to Diesel - the high excess of air during combustion makes the oxygen react with the nitrogen, forming NOx. The leaner, the more NOx. NOx emissions can be reduced by SCR or adsorber catalytic converters, but since VW, we know it's not that easy.
    – sweber
    Commented Jan 13, 2017 at 8:37
  • 2
    @sweber - Maybe you're just simplifying? Excess NOx is formed during a lean burn condition due to high combustion temperatures. I believe the figure is ~1700°F where normal combustion temps are ~1100-1200°F (that is IIRC). That would keep your combustion chambers clean, but would definitely pollute the air! :o) Commented Jan 13, 2017 at 13:16
  • @sweber I am convinced that lean burn does produce more NOx per unit of gas. But is it really worse per mile in cars like the Civic VX? The VX gets 44-50 MPG depending on driving skill. But the non-lean burn civics from the same years only get 30-35.
    – user25009
    Commented Jan 13, 2017 at 16:22


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