Demand is the gas. If you want the car to go farther, add gas.

That is, if you want to goose the economy, do something to increase demand, like increase government spending or provide help for the poor, who are most likely to use any help to increase spending locally. Rich people are more likely to just invest overseas.

Capital is the oil. There are *rare* times when capital is low, and supply cannot meet demand because businesses can't get off the ground without money to make it happen. That's like a car with very low oil. In those rare cases, adding oil helps the carbon better. I.e., adding capital helps make the economy run smoother, it makes it easier to start businesses to meet demand.

Thing is, we haven't really had a major problem with too little capital in the past half century. I'm sure you've all noticed that there are plenty of billionaires with tons of money and new businesses get started all the time and existing businesses expend and so on. We're just not short on capital.

Adding oil to a car that already has plenty of oil doesn't do anything but make the car stink.