Consumption of oil would negatively affect Saudi Arabia's and Iraq's economy.
Currently, Oil make up around 40% of Saudi Arabia's Gross Domestic Product, and around 60% of Iraq's Gross domestic product. This means that both of these countries are heavily depended on oil for their national income.
If other countries stopped using as much oil as they do, a lot of oil companies in both of these countries would be forced to cut down the total amount of their workers.
This would lead to an increase in Unemployment and a decrease in average disposable income for the citizen.