For traditional ICE cars, the amount of gas you burn is largely correlated to the RPM's of the engine when acceleration isn't happening. Since ICE cars have ge

For traditional ICE cars, the amount of gas you burn is largely correlated to the RPM's of the engine when acceleration isn't happening. Since ICE cars have gears, you'll have worse MPG efficiency while idling in 1st gear going 3 MPH, when compared to idling in a higher gear at a faster MPH. Most ICE cars can almost (but not quite) idle in a high gear at around 40MPH. So yes, going too slow can hurt gas mileage. Its a different matter for hybrids and EVs though...