What is the difference between Castrol 30 and 40?
3 Answers
The numbers 40 and 30 after 5W represent viscosity, with higher numbers indicating greater viscosity and suitability for higher maximum temperatures. In other words, 5W40 can adapt to higher temperature environments compared to 5W30, and higher viscosity oils (with higher values) may also be more suitable for high-speed driving or heavy-duty vehicles. Relevant information about engine oil is as follows: 1. Introduction: Engine oil, also known as engine lubricant (English name: Engine-oil), has a density of approximately 0.91×10³ (kg/m³). It serves to lubricate and reduce wear, assist in cooling, seal against leaks, prevent rust and corrosion, and provide shock absorption for the engine. It is often referred to as the 'blood' of a car. 2. Composition: Engine oil consists of two parts: base oil and additives. The base oil is the main component of lubricating oil, determining its basic properties, while additives compensate for and improve any shortcomings in the base oil's performance, imparting new characteristics, making them an essential part of lubricating oil.
I just researched this when changing my car's oil. The main difference between Castrol 30 and 40 is viscosity - the higher the number, the thicker the oil. 30-weight flows better, lubricating the engine faster during cold starts, making it ideal for northern winters or frequent short commutes. 40-weight forms a thicker oil film, providing extra protection for prolonged high-speed driving or older engines. After my car hit 120,000 km, I switched to 40-weight and noticed reduced engine noise. Always check your owner's manual for recommended viscosity - Japanese cars typically use 30-weight, while German turbocharged vehicles often require 40-weight. In ambient temperatures exceeding 40°C, 40-weight offers more stable performance.
30 and 40 refer to the high-temperature viscosity grades of engine oil. Simply put, 40-weight oil is thicker than 30-weight when the engine operates at high temperatures, offering better protection but slightly higher fuel consumption. I noticed during oil changes that 30-weight is suitable for daily commuter cars, especially those with auto start-stop systems, as it provides less resistance during cold starts and better fuel efficiency. 40-weight is more suitable for performance vehicles or high-mileage cars, ensuring the oil film won't break down even when the engine runs hot during long summer drives. Remember, viscosity standards vary by brand—Castrol's 30 might actually be thicker than other brands' 30-weight oils. Don't just look at the grade; also check manufacturer certifications like API SP or European ACEA standards.
