That's 80k km if you live somewhere where electricity comes 100% from coal, where I live with hydro it's under 20k km. You're also making an assumption without knowing how much that 8k km emits with their gas car.

To give an example with numbers...

Gas car produces 5 tons of CO2 when being manufactured and then emits 1 ton a year driving 8k km

Electric car produces 10 tons of CO2 when being manufactured then emits 0.25 tons a year driving 8k km

After 6 ⅔ (we'll round it up to 7) years the EV compensated for the extra CO2 required for its production and has emitted 10 + (7 x 0.25) = 11.75 tons of CO2. Meanwhile the gas car has emitted 5 + (7 x 1) = 12 tons of CO2 and the difference will keep increasing.

As for the battery failure scare, it's a non issue with the vast majority of models and it ignores the extra maintenance required on the gas car that also pollutes.