Instead of electric cars, use of alternate sources of energy like solar cars would affect the oil industry more and are more environment friendly ways of transportation. Affect on oil industry will affect the economy of few countries badly as they need to find alternate sources of income.
Yes, nowadays oil has more than one opponent although they all may decrease use of oil and also we cannot measure effect of one factor on oil.
With the days of increasing economy, now the price of oil has increased again. So such huge fluctuations happening often truly affects economy. So an alternate source is required which can be electricity.