ACEA, API and OEM approvals, explained
In short
ACEA is the European engine oil classification — A/B classes for petrol and diesel engines without a particulate filter, C classes with reduced ash for cars with a DPF or GPF, E classes for trucks — while API is the American equivalent, with S grades for petrol (SN, SP) and C grades for diesel. Above both sits the carmaker's own approval, such as VW 504.00, MB 229.51 or dexos, and that is the specification which must match your owner's manual exactly.
Why viscosity alone is not enough
Viscosity — 5W-30 or 10W-40 — tells you how easily the oil flows when cold and when hot. It says nothing about the chemistry: which detergent package is inside, how well the oil neutralises acids, how it resists oxidation, how much ash it leaves behind after combustion, or whether it protects the catalytic converter. Two 5W-30 oils can be completely different products. One may be formulated for an American petrol engine, another for a European diesel with a particulate filter, a third for very long drain intervals on a VAG engine. All three print 5W-30 on the front. That is why the manual always asks for two things: a viscosity and a specification. The first is chosen with the engine and the climate in mind; the second is not negotiable at all. The rest of this article explains what each family of specifications means and how to check them.
ACEA: the A/B, C and E classes
ACEA is the European automobile manufacturers' association, and its classification is the most relevant one for Moldova's fleet, which is predominantly European. The A/B classes — A3/B4, for example — cover petrol and diesel engines without sensitive exhaust aftertreatment. They carry a normal level of ash-forming additives, a good detergency reserve and, in the case of A3/B4, stable viscosity at high temperatures. They are typical of cars from the 1990s and 2000s. The C classes — C1, C2, C3, C4, C5 — are the low SAPS oils, with reduced sulphated ash, phosphorus and sulphur. They are mandatory for cars with a particulate filter and modern catalysts. They differ from each other not only in ash level but also in high-temperature viscosity, which is why a C2 does not automatically replace a C3. The E classes are meant for heavy-duty diesel engines with long intervals and high soot loading. They have no place in a passenger car unless the manual explicitly calls for them.
API: the S and C series, and what SP adds
The American API classification uses two series. The letter S followed by a second letter marks oils for petrol engines, and the series has advanced alphabetically: SL, SM, SN, with SP as the most recent mainstream category. The letter C with a number and letter marks oils for commercial diesel engines. Newer categories in the S series generally cover the requirements of the older ones, so an API SP oil normally replaces an SN. SP was introduced above all for protection against low-speed pre-ignition, a phenomenon affecting small turbocharged direct-injection petrol engines — a type that has become extremely common in recent years. Beware of a frequent confusion: API and ACEA measure different things and do not substitute for one another. An API SP oil is not automatically an ACEA C3, and if the manual asks for ACEA C3, a label that only mentions API SP is not an answer.
Manufacturer approvals: the criterion that decides
Above the general classifications sit the carmakers' own approvals. These are additional test programmes, run on specific engines, and oils that pass them earn the right to print the approval number on the packaging. The ones most often seen here are VW 502.00, 505.00, 504.00 and 507.00; Mercedes-Benz 229.5, 229.51 and 229.52; BMW Longlife-01 and Longlife-04; GM dexos1 and dexos2; Renault RN17; PSA B71 2290 and 2312; Ford WSS-M2C. If the manual demands such an approval, it takes absolute priority over any other information on the can. An oil can be excellent and expensive and still be wrong for your car, simply because it lacks the required approval. Importantly, the relationship between them is not a hierarchy. VW 507.00 is not simply better than 502.00 — it is a low-ash oil for engines with a particulate filter, and it can be unsuitable in an older engine that requires 502.00.
How to check a can in 60 seconds
Start from the car, not from the shelf. Open the manual at the lubricants section, or look at the oil filler cap, where many cars print the specification directly. Write down the viscosity and the exact specification, numbers included. Then turn the can around and read the back label, not the slogan on the front. Look for the lines beginning with ACEA and API, and below them the approvals list. Compare letter by letter and digit by digit. Pay attention to wording. Text such as meets the requirements of or recommended for describes a claim made by the oil producer. A licensed approval appears simply as a number in the approvals list. Both can be legitimate, but if the car is under warranty, only the explicit approval is safe. Check the batch or fill date too. Stored properly, oil keeps for a long time, but a can that has spent years in wide temperature swings is not a bargain.
The mistakes that cost the most
First and most expensive: an A/B class oil with normal ash content in a car with a particulate filter. The ash does not burn off during regeneration — it settles in the filter permanently and visibly shortens its life. The effect does not appear immediately but after tens of thousands of kilometres, as increasingly frequent regenerations and ultimately a clogged filter. Second: assuming a higher number means a superior, backward-compatible class. In manufacturer approvals the numbers describe different families, not quality steps. Third: changing the specification in order to claim a longer drain interval. Long intervals are tied to particular oils; they are not inherited. If you are unsure what your car requires, the simplest route is to call us on +373 22 009 350 with the VIN. We will check the specification and tell you which options cover it from stock at our warehouse in Chișinău.
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Frequently asked questions
What does low SAPS mean?
It means reduced sulphated ash, phosphorus and sulphur. These elements come from the oil's additives and, on cars with a particulate filter and catalyst, they accumulate in the exhaust aftertreatment system. ACEA C class oils are formulated specifically to limit that effect.
Can an ACEA C3 oil replace a C2?
Not automatically. The C classes differ in high-temperature viscosity as well as ash level, and some engines are calibrated for a thinner oil. Stick to the exact class listed in the manual.
If the can carries the required approval, does the brand still matter?
The approval is the decisive technical criterion, because it was earned through engine testing. The brand accounts for formulation differences and production consistency, but any oil legitimately carrying the required approval is a correct choice for that engine.