Two bottles can both say 5W-30 and still be made for very different engines.
That is where many oil choices go wrong. The 5W-30 label tells you the oil’s viscosity grade. It does not tell you the full story about engine protection, fuel economy, emissions-system compatibility or manufacturer requirements.
So, an ILSAC GF-7A 5W-30 is not automatically the same as an ACEA C2, C3 or A3/B4 5W-30.
Here’s what you need to do: Choose an oil that matches all the requirements in your vehicle handbook, including the viscosity grade, the oil standard, and any car-maker approval.
GF-7 vs C2 vs C3 vs A3/B4 Compared
| Specification | Main focus | What to know |
| ILSAC GF-7A | Modern petrol engines | Focuses on fuel economy, wear and deposit protection |
| ACEA C2 | Petrol and diesel engines with emissions systems | Lower HTHS requirement than C3 |
| ACEA C3 | Petrol and diesel engines with emissions systems | Higher HTHS requirement than C2 |
| ACEA A3/B4 | Petrol and light-duty diesel engines | Different oil category from C2 and C3 |
The main point is that these specifications are not interchangeable just because the bottle says 5W-30.
Why Can Two 5W-30 Oils Be Different?
Think of 5W-30 as only one part of the oil’s description.
The viscosity grade tells you how the oil flows at lower temperatures and how it behaves when the engine is hot. This specification tells you much more about what the oil has been designed and tested to do.
For example, a modern turbocharged petrol car and a European diesel with a particulate filter may both use 5W-30. But they may require completely different oil specifications.
That is why choosing oil by viscosity alone can lead to the wrong product.
What is ILSAC GF-7 5W-30 Oil?
ILSAC GF-7 became effective in 2025 for petrol passenger-car engine oils. GF-7A covers common viscosity grades including 5W-30, while GF-7B is limited to 0W-16.
GF-7A was developed for newer petrol-engine needs. It includes requirements linked to fuel economy, engine cleanliness, timing-chain wear and protection against low-speed pre-ignition, often called LSPI.
LSPI can be a concern in some turbocharged direct-injection petrol engines, so the oil specification can be especially important in these applications.
For vehicles that call for this type of oil, Eco G 5W30 is one option that meets ILSAC GF-7 requirements.
As always, check the vehicle handbook first to make sure the specification is suitable for your engine.
What is ACEA C2 5W-30 Oil?
ACEA C2 is used in certain petrol and diesel engines, including vehicles fitted with exhaust after-treatment systems.
One of the main differences between C2 and C3 is HTHS viscosity. This is a measure of how the oil behaves when it is hot and under heavy load.
ACEA C2 has a lower minimum HTHS requirement than C3. This can support fuel-efficiency targets in engines designed for that type of oil.
The key word is “designed”. A C2 oil should be used where the manufacturer calls for C2.
Some 5W-30 oils are formulated to meet more than one ACEA category. Eco Universal 5W30 is suitable for applications requiring either ACEA C2 or C3, provided the vehicle manufacturer allows that specification.
What is ACEA C3 5W-30 Oil?
ACEA C3 is also used in many petrol and diesel engines with emissions-control systems.
The main difference from C2 is that C3 has a higher minimum HTHS requirement. In simple terms, it is designed to maintain a thicker oil film under high heat and load.
That does not make C3 automatically “better” than C2.
If an engine is designed for C2, changing to C3 without checking the manufacturer’s requirements is not always the right move. The two specifications are intended for different applications.
For vehicles that require ACEA C3, PX Euro 5W30 is designed for that type of application.
What is ACEA A3/B4 5W-30 Oil?
ACEA A3/B4 belongs to a different oil category from C2 and C3.
It is used in certain petrol and light-duty diesel engines and is designed around different performance requirements. It also has a higher HTHS requirement, similar to C3, but that does not make the two specifications interchangeable.
Another difference is the way these oils are designed around emissions systems. C2 and C3 belong to ACEA’s C categories, which are intended for compatible engines using modern exhaust after-treatment equipment.
A3/B4 should therefore not replace C2 or C3 simply because the viscosity is the same.
Which 5W-30 Specification Does Your Car Need?
Start with the owner’s manual or the vehicle manufacturer’s service information.
Check three things:
- The viscosity grade, such as 5W-30
- The required specification, such as GF-7A, C2, C3 or A3/B4
- Any manufacturer approval, such as a BMW, Mercedes-Benz or Volkswagen specification
Do not rely only on terms such as “fully synthetic”, “European” or “fuel efficient”. Those descriptions do not replace the actual oil specification.
The LSA Oils Lube Guide can help narrow down suitable oils by vehicle. The product details should still be checked against the vehicle manufacturer’s requirements.
Frequently Asked Questions
Can I use C3 instead of C2 if both are 5W-30?
Not automatically. C2 and C3 have different performance requirements. Use the specification listed by the vehicle manufacturer.
Is GF-7 better than ACEA C3?
No. They are different standards designed for different engine requirements.
Is 5W-30 suitable for diesel engines?
Yes, in many cases. But the required ACEA or manufacturer specification must also match the engine.
What does mid-SAPS mean?
It refers to controlled levels of sulphated ash, phosphorus and sulphur. These limits help make certain oils suitable for engines with modern emissions systems.
Can I choose engine oil by viscosity alone?
No. Two oils can both be 5W-30 but still be designed for different engines. Always check the full specification as well as the viscosity.
