Should the Sonata VIII use 40 or 30 engine oil?

[LaylaLynn]

It is recommended to use 30 engine oil. Engine oil selection: Naturally aspirated engines have relatively modest requirements for oil quality and can use mineral oil or semi-synthetic oil. If the owner has a larger budget, full synthetic oil can be used. Compared to naturally aspirated engines, turbocharged engines have a more compact structure and operate under harsher conditions, requiring higher oil performance. They need oil with better fluidity, and full synthetic oil is the best choice. Brand selection: For lubricant brand selection, if you prioritize long-lasting oil performance, you can choose Mobil lubricants; if you prioritize the oil's engine cleaning ability, Shell engine oil is recommended; if you need lubricants with strong oil film toughness, you can choose Castrol. For example, turbocharged engines are prone to carbon deposits during high-speed operation, so Shell engine oil with strong cleaning capabilities can be selected.

[LeLaila]

Recently tested two types of oil: After switching to 5W-30, idle speed dropped by 80 RPM and vibration in N gear reduced. The 40 oil showed noticeable degradation after 5,000 km, with engine sound becoming scattered. Older Korean cars have tighter piston ring designs, making high-viscosity oil less effective for oil film formation. For cars manufactured before 2016, 30 oil is recommended unless severe oil burning occurs, then consider 40. Note: If the oil cap is labeled 'API SN', use corresponding 30 oil; if labeled 'SM', 40 oil is acceptable. For frequent congested driving, 30 oil is better for faster heat dissipation and less carbon buildup.

[VanMolly]

Twenty years of experience running a repair shop: The eighth-generation Sonata's engine lasts longer with 30-weight oil. I've seen cars using 40-weight oil - after three years, the engine sludge when opened up looked like cracked earth. 30-weight oil has better cleaning properties and can remove piston ring carbon deposits. Be careful not to buy counterfeit oil - check the anti-counterfeit code on the official website. For long summer trips, you can mix in 10% 40-weight oil for enhanced protection, but don't switch directly to 40-weight. Had a customer who ignored this advice and switched to 40-weight - two months later, the VVT solenoid valve seized up, costing 800 yuan to fix. Judge by oil consumption - only consider increasing viscosity if consumption exceeds half a liter per 5,000 kilometers.