Is 30 or 40 better for engine oil in the south?

[SanMelanie]

5w30 is better for engine oil in the south. Compared with 10w40, 5w30 has better cold start performance and lower viscosity, while 10w40 has poorer cold start performance and higher viscosity. Advantages of viscosity: higher viscosity oil has better sealing performance, but the engine will consume more fuel. At idle, higher viscosity oil results in lower noise, while under driving conditions, higher viscosity oil leads to higher noise. Lower viscosity oil has the characteristic of fuel efficiency. Recommendations for cold weather use: If SAE10W-30 or higher viscosity engine oil is used in cold weather, the engine may be difficult to start, so it is recommended to use SAE0W20, 5W20, or 5W30 engine oil. Relatively speaking, using 0W-20 oil can maximize fuel savings.

[VanElla]

I've been driving in the south for over a decade where it's scorching hot, so you gotta be smart about choosing engine oil. 30-weight oil is thinner, flows smoothly when temperatures rise, offers better fuel economy, saves gas and money. Running the AC while driving in southern cities during summer, the engine operates more effortlessly with it. 40-weight is a bit thicker, provides stronger engine protection against wear at high temperatures, especially if you frequently drive on highways or carry heavy loads. But most southern regions are warm year-round, 30-weight is sufficient. My experience in Guangdong or Fujian shows 30-weight oil works just fine. The key is to check your car manual's recommendation—don't improvise. By the way, the south is rainy and humid, oil degrades faster. I suggest checking/changing oil every 5,000 km or 6 months, synthetic types handle heat better to avoid engine issues and extended maintenance cycles.

[AmeliaLee]

From a cost-saving perspective, I need to be meticulous when choosing engine oil for daily commuting in the south. 30 viscosity is usually cheaper, offers lower fuel consumption, and allows more mileage per liter of oil, helping to cut costs; 40 viscosity is more expensive but more durable, provides better high-temperature protection, and can extend the oil change interval. In the south, the heat can cause oil to oxidize and thin, so 40 might last longer. However, on balance, I think 30 is more economical, especially for city driving with small-displacement cars. Don't forget that oil brands affect prices—brands like Mobil or Castrol vary significantly, so just pick a reliable one. The southern climate is humid, so don't just focus on saving small amounts of money. Frequent oil changes are a priority for safety—check every six to seven thousand kilometers to extend engine life and avoid costly major repairs.

[Ava]

I've helped many friends choose engine oil. In the hot southern climate, simply put, choosing between 30 and 40 is like selecting between thin and thick clothing. 30 is thinner, offering faster heat dissipation and better fuel efficiency; 40 is thicker, providing stronger protection against heat damage. Beginners shouldn't overthink it—most cars are fine with 30, especially modern sedans for hassle-free use. In the humid and hot south, 30 flows better for smoother starts and stops; consider 40 only for older cars or those frequently under heavy loads like SUVs. Checking the car manual is the most reliable method, and always look for the SAE number on the oil label. Remember to choose heat-resistant synthetic oil when changing, and check the oil color every 5,000 kilometers—if it darkens, it's time to change. Don't delay to avoid causing issues.