What “compatible” means here
A compatible upgrade means an official category source says a later category includes or can service the earlier category’s performance requirement within the same track. It does not mean every oil carrying that category fits every vehicle. The candidate still needs the manual’s SAE viscosity, named manufacturer specification or approval, fuel and emissions-system application, market and service conditions.
“Same standard” confirms only that the category labels match. “Older standard” means the candidate sits earlier in an explicit backward-compatible track. “Separate category” means no upgrade direction applies between the tracks. “Conditional” is used for ACEA profiles or a viscosity conflict. Cross-family labels return “unsupported comparison” because the systems measure different requirements.
How API, ILSAC, diesel and ACEA standards differ
API gasoline service categories use an S-prefix and a documented later-to-earlier direction. ILSAC passenger-car standards combine performance and fuel-economy requirements but split into a main A track and a 0W-16-only B track. API diesel has a C-category succession plus the separate FA-4 category. ACEA light-duty categories describe application profiles; their letters and numbers do not create one universal newest-to-oldest ladder.
API gasoline: SQ, SP, SN PLUS and SN
The explicit comparison direction used here is SQ → SP → SN PLUS → SN → SM → SL → SJ. A category on the left can cover a requirement to its right when every remaining vehicle requirement matches. The reverse direction is not an upgrade.
API SQ versus API SP
API’s Motor Oil Guide lists SQ as the current gasoline category introduced in March 2025 and SP for 2025 and older automotive engines. The guide’s general gasoline statement allows the latest category to service earlier-category recommendations. For a deeper source walkthrough, read API SQ vs. API SP.
API SP versus API SN and SN PLUS
SP is later than SN. API also states that SP oils include all SN PLUS requirements; SN PLUS originally identified SN oils meeting a higher performance level. That makes SP a compatible category upgrade for an SN or SN PLUS requirement, subject to the manual’s other conditions. An SN or SN PLUS oil is not treated here as a replacement for SP.
ILSAC uses two separate tracks
The main track is GF-7A → GF-6A → GF-5 → GF-4 → GF-3 → GF-2 → GF-1. The 0W-16-only track is GF-7B → GF-6B. Cross-track comparisons return a separate-category result rather than guessing equivalence.
API’s current guide records GF-6A and GF-6B as current through September 30, 2026 and obsolete on October 1, 2026. The dataset stores that transition date so the warning changes with the date instead of permanently hardcoding either status. GF-7B can service a GF-6B requirement only in the 0W-16 track.
API diesel: CK-4, CJ-4 and FA-4
Within the C-category track, the checker uses CK-4 → CJ-4 → CI-4 PLUS → CI-4 → CH-4. API says CK-4 exceeds the listed earlier categories, while CJ-4 exceeds CI-4 with CI-4 PLUS, CI-4 and CH-4. Fuel sulfur, aftertreatment and drain-interval conditions can still change the application.
FA-4 versus CK-4
FA-4 is not the next step after CK-4. API states that FA-4 is not interchangeable or backward compatible with the C categories in this checker. It identifies certain XW-30 oils for select engines, so the result always retains an engine-manufacturer-permission warning.
ACEA categories are not a hierarchy
The 2023 ACEA light-duty sequence defines A3/B4, A5/B5 and A7/B7 high-SAPS profiles and C2 through C7 aftertreatment-compatible profiles. Different entries can have different HTHS viscosity, SAPS, fuel-economy and engine-test requirements. ATIEL says combined claims are possible only when all associated chemical limits and physical testing requirements are met. A higher number alone does not authorize substitution.
ACEA C2 versus C3
ACEA C2 specifies a minimum HTHS viscosity of 2.9 mPa·s; C3 specifies a minimum of 3.5 mPa·s. Both are mid-SAPS aftertreatment-compatible profiles, but they are not the same requirement. The oil label must make the claim you rely on, and the vehicle manufacturer must allow the category and viscosity.
ACEA C7 is a 0W-16 category based on C6 performance with enhanced fuel economy. A non-0W-16 viscosity input therefore creates a conflict warning rather than a positive result.
OEM specifications remain vehicle-specific
This release does not accept BMW, Mercedes-Benz, Volkswagen, dexos or other manufacturer specifications as inputs. A vehicle can require both an industry category and a separate manufacturer claim. Learn how to distinguish OEM approval from “meets requirements”, review the Volkswagen specification system, or see the BMW oil-selection process.
If a top-up or emergency situation is driving the comparison, read the limits on mixing engine oils. For the wider selection process, use the four checks for choosing engine oil.
Supported standards
The comparison controls include the standards below. Older API gasoline SH through SA and diesel CG-4, CF-4, CF-2 and CF are shown as informational obsolete entries only; they are intentionally excluded from comparison until pair-level rules are reviewed.
| Family | Track | Comparison choices |
|---|---|---|
| API gasoline | Gasoline | SQ, SP, SN PLUS, SN, SM, SL, SJ |
| ILSAC | Main A | GF-7A, GF-6A, GF-5, GF-4, GF-3, GF-2, GF-1 |
| ILSAC | 0W-16 B | GF-7B, GF-6B |
| API diesel | C category | CK-4, CJ-4, CI-4 PLUS, CI-4, CH-4 |
| API diesel | F category | FA-4 |
| ACEA light-duty | Profiles | A3/B4, A5/B5, A7/B7, C2, C3, C4, C5, C6, C7 |
Methodology
- Use only standards named by the current API consumer guide or ACEA 2023 light-duty sequence.
- Store every selectable within-family required/candidate direction as an explicit rule; do not compare letters or numbers programmatically.
- Attach each rule to a source record, locator, conditions, reviewed explanation template and check date.
- Return no cross-family direction and no general ACEA hierarchy.
- Apply lifecycle and viscosity warnings after the category result so an obsolete requirement or input conflict is never hidden.
The matrix was researched and authored by Dzianis Kuziomkin and OilFinderPro’s editorial workflow. No separate technical reviewer is named. To report an error, use the corrections process or email support@oilfinderpro.com.
Sources
- American Petroleum Institute, API's Motor Oil Guide, 2025-04-21. Motor Oil Guide, pages 2–4: PLUS classifications, gasoline, ILSAC and diesel category guidance. Accessed July 28, 2026.
- American Petroleum Institute, API Oil Categories, Current web guidance. Gasoline Engines and Diesel Engines category tables. Accessed July 28, 2026.
- European Automobile Manufacturers' Association (ACEA), ACEA Oil Sequences 2023 – Light-duty Engines, 2023, Revision 0 (September 2023). Pages 3–4, consumer language for A/B and C categories; pages 5–10, category limits. Accessed July 28, 2026.
- ATIEL, ACEA Oil Sequences – Performance Claims, ACEA 2023 light-duty claim guidance. Combined Claim, Incompatible Claim and Valid Compatible Claims sections. Accessed July 28, 2026.
Frequently asked questions
Can a newer API gasoline category replace an older one?
Usually within the explicit API gasoline track: for example, API SQ can service an API SP requirement. The SAE viscosity and every vehicle-manufacturer requirement must still match.
Can I use ILSAC GF-7B instead of GF-6A?
No automatic substitution applies. GF-7B is in the 0W-16-only B track, while GF-6A is in the main A track. Use the exact track and viscosity required by the vehicle manufacturer.
Is API FA-4 backward compatible with CK-4?
No. API states that FA-4 oils are not interchangeable or backward compatible with CK-4 and the listed earlier C categories. FA-4 is limited to certain XW-30 oils for select engines and needs manufacturer permission.
Is a higher ACEA category number always better?
No. ACEA light-duty categories are different application profiles, not one universal hierarchy. Match the exact category, viscosity and manufacturer specification in the owner’s manual.
Can ACEA C3 replace ACEA C2?
Not by category name alone. The 2023 ACEA sequence gives C2 and C3 different HTHS viscosity profiles. Use C3 for a C2 requirement only when the vehicle manufacturer allows it and the product makes the needed claims.
Does a compatible API, ILSAC or ACEA result replace an OEM approval?
No. A category result does not replace a named manufacturer approval, SAE viscosity, market-specific requirement or application limit. Check the owner’s manual and the oil label.