Right, here's a crash course in engine oil labels (just the official industry body ones, not the OEM specs, 'cos that's a whole load more stuff);

API ones are easy. They are American, but recognised across the world. API stands for American Petroleum Institute. Their specs are fairly logical to understand. Anything starting with an S means Spark, anything with a C means compression, so therefore gasoline and diesel respectively. Then with each generation of spec they have gone a letter higher in the alphabet, but retain back-compatibility to anything that has gone before it. So in the instance given below, Drivetec CF & CG-4 > Wilko CF-4 > Havaline CF.

The ACEA nomenclature is much less logical. (ACEA is the European automobile manufacturers association, from the French “Association des Constructeurs Européens d' Automobiles”).

ACEA are much more specific in what the performance of the oil actually is. A = Petrol, B = Diesel and C = Catalyst compatible or low SAPS (Sulphated Ash, Phosphorus and Sulphur).

Unlike API the ACEA specs are split into performance/application categories as follows:

• A1 Fuel economy petrol
• A2 Standard performance level (now obsolete)
• A3 High performance and/or extended drain
• A4 Reserved for future use in certain direct injection engines (so ignore this one)
• A5 Combines A1 fuel economy with A3 performance

• B1 Fuel economy diesel
• B2 Standard performance level (now obsolete)
• B3 High performance and/or extended drain
• B4 For direct injection car diesel engines
• B5 Combines B1 fuel economy with B3/B4 performance

• C1-04 Petrol and Light duty Diesel engines, based on A5/B5-04 low SAPS, two way catalyst compatible.
• C2-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two way catalyst compatible.
• C3-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two way catalyst compatible, Higher performance levels due to higher HTHS.

Put simply, A5/B5 > A3/B3 » A2/B2 (while C3 oils are the better quality, stay in grade performance oils).

So in the example, the A3 / B3 of the Wilko and Drivetec are equivalent and both better than the lower standard of the Havaline with its very basic A2/B2 claim. The extra ACEA E7 claim on the drivetec oil is part of a whole extra 'E' series of ACEA specs for heavy-duty diesel engines. So it might be of interest to Truck owners, but not to people running about in a Freelander. (E7 is a reasonable level of performance by the way).

As a general rule though, check the manufacturer's recommendation for your vehicle and pick one that meets what it specifies. If it references an API spec, make sure you choose something at least as high in the alphabet. If it's ACEA for a car, consult the table above.

Hope that helps.