Electric cars being charged by fossil fuels still have major advantages. Those who make generators are incentivized to get as many joules of energy per gallon of fuel. Diesel generators can have some efficiency adaptations that vehicle engines wont often have, such as being designed to run at a fixed speed. Your average car owner wont care about efficiency as much as getting from point A to point B, so the already low efficiency of combustion engines is probably lower on average than what could be theoretically achievable just due to people not maintaining their vehicles. Electric vehicles do not idle, and starting an electric vehicle does not cost extra power. Additionally, stop and go traffic leads to far less loss of energy in cities for anyone driving an electric vehicle.

While I would prefer renewable power for electric vehicles, electric cars can still use fossil fuel power more efficiently than internal combustion engines can.

I’d still prefer electric trains however.