Which is of a higher grade, engine oil C3 or A3B4?

[JamesDella]

Both engine oil C3 and A3B4 are standards rated by the European Automobile Manufacturers' Association (ACEA). The difference between them mainly lies in their series. Engine oil A3B4 belongs to the higher-grade mainline lubricants, where 'A' represents gasoline engines for passenger cars, and 'B' stands for diesel engines. Engine oil A3B4 is suitable for gasoline and light-duty diesel engine oils, while engine oil C3 is designed for catalyst-compatible engine oils, specifically for diesel engine models equipped with DPF (Diesel Particulate Filter). Below is relevant information about C3 engine oil: C3 engine oil has two main characteristics: first, C3 engine oil has a very low TBN (Total Base Number), making it an environmentally friendly oil; second, the shear value of C3 engine oil is all greater than 3.5, making it particularly suitable for German engines, especially those of Volkswagen, Audi, Mercedes-Benz, and BMW. Disadvantages: C3 engine oil cannot coexist with ethanol gasoline. Ethanol gasoline can emulsify the engine oil, dilute the oil film, and to some extent, render the anti-wear additives ineffective. During the use of ethanol gasoline, acetaldehyde and acetic acid can form and enter the engine oil, diluting the TBN of the engine oil and affecting its cleaning and dispersing capabilities, thereby shortening the replacement cycle of C3 engine oil.

[VanAdeline]

I've been driving for over a decade and have used many engine oils. Both C3 and A3B4 are European standard oil specifications, but C3 is of a higher grade. Simply put, C3 belongs to the low-ash category, specifically designed for vehicles with emission systems, such as modern diesel cars equipped with particulate filters; A3B4 is more versatile, suitable for older gasoline or diesel engines without advanced emission control devices. Why is C3 of a higher grade? Because it's more environmentally friendly and offers better protection for components, such as reducing carbon buildup and extending turbocharger life, especially popular under the Euro 6 emission standards. I recommend checking the owner's manual when choosing oil—newer cars usually require C3, while older cars can get by with A3B4. Don't mix different oils, as it can cause problems. These maintenance details are crucial, affecting engine longevity.

[NathanRose]

As someone who frequently tinkers with engines, I must say the C3 specification is more advanced than A3B4. Both are ACEA standards, with C3 targeting low-ash performance, meaning reduced ash residue to protect exhaust treatment systems like DPFs; A3B4 is more basic, designed for mid-ash levels without emphasizing emission protection. The higher grade is reflected in vehicle compatibility—modern high-efficiency engines or hybrid systems often require C3, while A3B4 is commonly used in classic models. I recommend regularly checking oil specifications carefully, especially for modified cars, as using the wrong type may clog filters or increase fuel consumption. Upgrading oil can enhance performance, but don't switch blindly—seek professional advice.

[MacElliott]

I've been working on cars since I was young, and I've seen many changes in oil specifications. The C3 grade is higher than A3B4. C3 is suitable for new cars with environmental protection systems, as it has low ash content and is less likely to clog the exhaust pipe; A3B4 is an old standard, suitable for ordinary engines. Don't change oil types too often when driving, just follow the manufacturer's recommendations. Don't skimp on maintenance to save small money, as it can save you big money in the long run.