I'm not sure that's practical, or even possible. There are over a billion cars in the world. Next thing you know we are killing ourselves via deforestation or starving ourselves by using too high a percentage of our arable land growing fuel instead of food. Beyond that though, there are also other HUGE hurdles. Every tire on every car in the world requires 7 gallons of petroleum to produce and they have to be replaced periodically. The paint on the car is petroleum based, all the plastic parts of the car are petroleum based and then you have to spend huge amounts of petroleum resources to build each car, which, like the tires, all have to be replaced periodically. It is a very complex problem that methanol will not solve.