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Old 11-26-2021, 02:27 AM   #111 (permalink)
Isaac Zachary
High Altitude Hybrid
Join Date: Dec 2020
Location: Gunnison, CO
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Avalon - '13 Toyota Avalon HV
90 day: 40.45 mpg (US)

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Originally Posted by JSH View Post
Gasoline and Diesel vehicles have been held to identical emission standards since 2010. HC and NOx are now bundled together so that doesn't give either fuel an advantage. CO2 standards are also identical.
The standards are the same, but what differnt kinds of engines are capable of can differ.

Gasoline engines are easy to clean up the NOx in because they are easy to run at a stoichiometric AFR.

But diesels are easier to clean up the CO and HC emissiions in because they have to run lean. Although I guess getting gasoline exhaust to burn up completely could be as easy as intalling an air pump to pump in air at some point before a catalyst to burn up the left over CO and HC emissions.

Historically diesels have gotten better energy per unit of CO2 released although it's not leaps and bounds better than Gasoline. However, some techniques that try to get gasoline engines to get as efficient as diesel engines make them produce more PM and NOx emissions (e.g. lean burn or direct injection)

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