Are engine oils A3B4 and A5B5 compatible?
2 Answers
Because gasoline and diesel vehicles are different, the types of engine oils they use have different viscosities and are not compatible. Mixing them can affect engine speed and the cooling reactions within the engine, so they should not be mixed to avoid chemical reactions. Relevant details are as follows: 1. Meaning: Engine oil A3B4 and A5B5 are two testing and certification standards set by the European automobile manufacturing industry for automotive lubricants, with A5B5 being the highest level in this certification standard. Here, 'A' refers to gasoline engines for passenger cars, 'B' refers to diesel engines for passenger cars, and the numbers indicate quality—the higher the number, the better the quality and the higher the grade. 2. Comparison: There are differences between A5B5 and A3B4 in terms of thermal-oxidative stability, anti-wear properties, detergency, dispersancy, and viscosity retention. Since A3B4 contains more additives than A5B5, it performs better in anti-wear properties. However, A5B5 has higher requirements for fuel economy, reflecting its better fuel efficiency and being more economical in fuel consumption.
As a car enthusiast, I've researched quite a bit about oil specifications. Both A3/B4 and A5/B5 are ACEA European standards, but compatibility depends on the vehicle condition. A3/B4 oil has higher viscosity, making it suitable for high-load engines like older German cars, as it provides better component protection. A5/B5 has lower viscosity, focusing on fuel efficiency and environmental friendliness, and is ideal for newer models such as Japanese or European vehicles with start-stop systems. If your car's manual specifies A5/B5 and you suddenly switch to A3/B4, it may increase engine resistance, raise fuel consumption, and even accelerate wear. Conversely, using A3/B4 in a new car designed for A5/B5 could lead to excessive oil pressure, potentially causing seal leaks. I've examined several cases where mixed usage resulted in increased noise or reduced performance, so don't cut corners—checking the manual is key. New car owners who are unsure should consult a professional repair shop for an oil sample test—it's not a trivial matter, as it directly affects the vehicle's lifespan.
