Of all the classic cars, with a product scale of 1:18, which product is the most ordered product by customers?
classic car is a product line; most ordered product refers to MAX(quantityOrdered);
SELECT T1.productName FROM products AS T1 INNER JOIN orderdetails AS T2 ON T1.productCode = T2.productCode WHERE T1.productScale = '1:18' AND T1.productLine = 'Classic Cars' GROUP BY T1.productName ORDER BY SUM(T2.quantityOrdered) DESC LIMIT 1