Engine oil specifications
Every good product goes through certain certifications before they are approved for us. Car oils are no exception. Check carefully that the oil has been certified to meet certain specifications. A good oil should have ACEA and API ratings as these are the acceptable standard.
1. API specs
API stands for American Petroleum Institute while ACEA stands for Association des Constructeurs Europeens d’Automobiles.

API is very basic and easy to understand. It has two different categories for passengers. S = Petrol and C = Diesel. Most oils have both diesel (C) and petrol (S) specifications. Let’s take a look at the updates of the oil specifications!

SG: contains a high degree of functional dispersants that are resistant to black sludge
SH: has similar engine tests as SG but contains phosphorus limit 0.12% in addition to volatility, foam control and stability
SJ: Its engine test is the same as SG/SH, but it contains a phosphorus limit of 0.10% as well as volatility limit variations.
SL: This is mostly found in all new engine tests of modern day engines designed to align with the latest emission standards.
SM: It has advanced features such as oxidation resistance, wear protection, low performance temperature and deposit protection in comparison to the older categories.
CD: represents the international turbo oil engine standard for many years. It makes use of a single cylinder for engine testing.
CE: indicates an improved regulation of oil consumption as well as piston deposit and wears, oil thickening, and makes use of multi cylinder engines for testing.
CF4: shows continuous improvements in controlling oil consumption and deposit of pistons. It also makes use of emission test engines that are low.
CF: It’s the advanced CD version. It’s mainly used for indirect injection engines.
CF2: It’s the yardstick for defining accurate control of deposits in the cylinder and scuffing of the ring face.
CG4: Development of CF4 made way for continuous control of oxidation stability, piston deposits and soot entrainment.
CH4: Development of CG4 for better performance, is the result of more comprehensive engine tests involving either low or high-sulphur fuels.
CI4: conforms to 2004 emission standards, optional to systems with up to 0.5%-sulphur fuel or when CE, CD, CG4, CF4 or CH4 is required.

Specifications in use before the SL are no longer efficient. As a matter of fact, they have gone into extinction. For other specs apart from CH4 are still useful in older vehicles that are over 10 years old, their performance level and protection are nothing compared to the more recent specifications. In brief, the best oil specs are the most modern ones: SM, SL, CI4 or CH4.


2. ACEA specs
The ACEA is the European version of API in the US. It lays more emphasis on the specific oil performance. A = Petrol, B = Diesel and C = Catalyst Compatible or low Sulphated Ash, Phosphorus and Sulphur (SAPS).

Performance categories of the ACEA include:
A1 Economy petrol of fuel
A2 Performance level (standard)
A3 High performance
A4 Put aside for future use in some direct injection engines
A5 Uses both A1 fuel economy in addition to performance of A3
B1 Diesel fuel economy
B2 Performance level (standard)
B3 High performance
B4 Used on cars with direct diesel injections
B5 Uses fuel economy of B1 with performance of both B3 and B4
C1-04 Based on A5/B5-04 low SAPS, petrol & light duty diesel engine, 2-way catalyst compatible
C2-04 Based on A5/B5-04 mid SAPS, petrol & light duty diesel engine, 2-way catalyst compatible
C3-04 Based on A5/B5-04 mid SAPS, petrol & light duty diesel engine, 2-way catalyst compatible, higher HTHS, resulting in better performance
Regarding ACEA specs, car oils with A3/B3, A5/B5 or C3 index are of higher general quality compared to the rest of above list.

3. Other specs to look for on car oil bottle
Intended use
There are various car oils on the market. Each of them serves a unique purpose. You don’t just pick any oil and use it on your car without knowing if it’s suitable for that purpose. Doing that will worsen the situation, leaving you with more problems instead of a solution. Read what the oil is intended for, thoroughly, before taking it close to your car.

Oil Viscosity or simply the oil "thickness"
Single-grade engine oil is labeled one in 11 grades: 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50 and 60. The "W" symbol refers to "winter", meaning the dynamic viscosity of certain oil is measured at different ranges of cold weather. The lower the grade is, the lower temperature the oil passes. Non-winter lablel oil is measured at exactly 100 °C.

A good number of modern oils put up for sale are known as “Multi-grades.” This simply means that such oils belong to two different grades of oil, and noted in the form of 20W - 30. The concept of multigrading came into use about 50 years ago to stop car users from using different kinds of oils at different seasons.

OEM approvals and codes
OEM approvals and codes are important variables to look out for. If they are missing, the product is most likely not certified. Using such a product is at your own risk.

You will find several OEM’s on the bottle of oils. The most commonly used ones in the UK include BMW, VW or MB. But don’t assume that any oil that has them is authentic. Although recognized companies producing oils send their oils to OEMs to get the recommended approvals, some older specs can be created with cheap materials. Be on the look out for newer specifications as they are better by all standards.

What is the best oil for car engine?
There are many factors you need to consider in choosing the best oil for car engine. If you read thoroughly earlier parts, you can withdraw some basic lessons to find a suitable car oil bottle.

First, synthetic oil is considered better than conventional oil in many cases. It helps keep your engines cleaner, perform better and harder to break.

Second, oil products with certain API and ACEA specs have higher performance, conforming to modern vehicle standards, namely SM, SL, CI4 or CH4 (for API) and A3/B3, A5/B5 or C3 (for ACEA).

Steps to pick the right oil for your car:
1. Study the suggested oil weight and viscosity in your vehicle manual

2. Look for recommended oil type or even oil brand for your vehicle in the manual (if have)

3. Identify API or ACEA specs that suit your vehicle

4. Find the oil product with OEM codes and all above index/ specs.

Source: https://naijauto.com/car-maintenance/engine-oil-2056