CREATE TABLE table_23840623_4 (epa_rated_combined_fuel_economy VARCHAR2, vehicle VARCHAR2)

What is the epa rated combined fuel economy for the Nissan Leaf?
SELECT epa_rated_combined_fuel_economy FROM table_23840623_4 WHERE vehicle = "Nissan Leaf"
SELECT "epa_rated_combined_fuel_economy" FROM "table_23840623_4" WHERE "Nissan Leaf" = "vehicle"