In the article, the efficiency section give numbers for how effective the car is to extract energy from gasoline vs extracting energy from the electrical grid. They also give the efficiency of "fossil fuel power plant", but not oil specific.

IC car = 15-30%

Fossil fuel power plant = 50%

Electric car = output of power plant * 0.77

Taking the average we get: 22.5 for IC car, 38% for the electric car. A 15.5% more energy.

I have no idea if those numbers are correct because the website you linked does not straight up comparison between the oil being burned in a power plant and the oil being burned in a car, in order to travel a certain distance.

As a strategy for combating global warming, IC to EV has several numbers to consider. The benefit in the power grid which depend on the country in question. The growth rate of cars. One should also make a comparison to do a similar transition with the power grid itself. And finally the required reduction in emissions to prevent global warming.

My own conclusion is that we need to do both. Doing just IC to EV without removing fossil fuels from the power grid won't be enough. EV will make the car more efficient and allow for more cars on the same amount of emissions, but its an incremental improvement rather than a full stop in terms of emissions.