If you charge overnight, the base load is less likely to be fossil fuel. If it is fossil fuel, emission controls on a power plant are far more effective than anything with wheels.

The average car emits 400g CO2 per mile
epa.gov/…/greenhouse-gas-emissions-typical-passen…

My power company emits 364g per kWh, which will take an EV about 3 miles. So that’s about 120g CO2 per mile, about one third.
climatiq.io/…/65ad9f91-28a1-45b2-bbab-3dcdd5de6a4…