The mileage of a Royal Enfield Classic 350 before service can vary depending on several factors, including riding conditions, maintenance, and individual riding habits. On average, the Royal Enfield Classic 350 is known to deliver a mileage of around 35-40 kilometers per liter (km/l) of fuel in city riding conditions. However, during highway rides or if ridden at a constant speed, the mileage can slightly improve, reaching up to 40-45 km/l. It's important to note that these figures are approximate and can vary based on various factors. Regular maintenance, such as timely oil changes, proper tuning, and maintaining the correct tire pressure, can help optimize the motorcycle's mileage.