A3/B4 refers to the quality grade of engine oil and complies with the A3/B4 quality grade in the ACEA (European Automobile Manufacturers Association) classification. Grades starting with “A” represent the specifications for gasoline engine oils. Currently, they are divided into five grades: A1, A2, A3, A4, and A5. Grades starting with “B” represent the specifications for light-duty diesel engine oils and are currently divided into five grades: B1, B2, B3, B4, and B5.

The ACEA standards are upgraded approximately every two years. The latest standards are the 2016 version 0 (in 2016), version 1 (in 2017), and version 2 (in 2018). Correspondingly, the certification standards of various automobile manufacturers are also upgraded year by year. For the same Volkswagen VW 50200 certification and Mercedes-Benz MB 229.5 certification, it is also necessary to distinguish whether they have been upgraded to the latest standards. Those that are always willing to upgrade demonstrate self-discipline and the pursuit of quality and performance. Generally speaking, it is already good if engine oil can meet the certifications, and it may not always be willing to keep up with the upgrades.

ACEA C series are used for gasoline engines and light-duty diesel engines with after-treatment systems. Among them, ACEA C1 and C4 are low SAPS (Sulfated Ash, Phosphorus, and Sulfur) engine oil standards, while ACEA C2, C3, and C5 are medium SAPS engine oil standards.

The common point between the C3 and A3/B4 standards is that the High Temperature High Shear (HTHS) value is ≥ 3.5. The main difference is that one is of medium ash content while the other is of high ash content. That is to say, there cannot be an oil that meets both A3/B4 and C3 at the same time.

The core difference between the C3 and A3/B4 series lies in the element limits, mainly sulfur and phosphorus. They can cause the premature failure of the three-way catalytic converter, and excessive ash content can cause the failure of the DPF (Diesel Particulate Filter) in diesel cars. Therefore, European car manufacturers have set limits on these three indicators simultaneously, giving rise to the new C standards. The C series has been introduced for nearly 20 years. There are a large number of diesel cars in the European market, so this standard is highly targeted. However, in China, this may not be the case. 95% of passenger cars in China are gasoline-powered vehicles without DPFs, so the ash content limit is not of great significance. If your car doesn’t care much about the three-way catalytic converter, you can completely use A3/B4 oil. Gasoline cars that meet China’s National Standard V and below have no major problems using A3/B4 oil.

However, due to the introduction of GPF (Gasoline Particulate Filter) in China’s National Standard VI vehicles, the high ash content of A3/B4 oil has a significant impact, and the oil quality has thus been forced to upgrade to the C standards. There is another difference between A3/B4 and C3: that is TBN (Total Base Number). A3/B4 requires TBN > 10, while the C series only requires TBN > 6.0. There are two reasons for this. First, the decrease in ash content leads to a decrease in the base number, which can no longer be as high as before. Second, with the improvement of fuel quality, TBN doesn’t need to be that high anymore. In the past, when the fuel quality in China was poor, the high TBN of A3/B4 was very valuable. Now that the fuel quality has improved and the sulfur content has decreased, its significance is not as great. Of course, in regions with poor fuel quality, the performance of A3/B4 is still better than that of C3. The third difference lies in fuel economy. The A3/B4 standard has no requirements for fuel economy, while engine oils that meet both the ACEA C3 and API SP standards have strict requirements for fuel economy, camshaft protection, timing chain protection, and resistance to low-speed pre-ignition. To sum up, the most significant difference between A3/B4 and C3 is that C3 is a product with medium and low SAPS (ash content). In terms of other parameters, C3 can completely cover the applications of A3/B4 and meets the Euro VI and China’s National Standard VI emission standards.

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