CREATE TABLE table_15191 ("Year" FLOAT, "Entrant" TEXT, "Chassis" TEXT, "Engine" TEXT, "Points" FLOAT)

What was the engine of the Hoover Motor Express after 1955 with greater than 0 points?
SELECT "Engine" FROM table_15191 WHERE "Year" > '1955' AND "Points" > '0' AND "Entrant" = 'hoover motor express'
SELECT "Engine" FROM "table_15191" WHERE "Entrant" = 'hoover motor express' AND "Points" > '0' AND "Year" > '1955'