General educational information, not a product approval. Always confirm the current TDS, the equipment manual and the OEM requirement before ordering.
CH-4, CI-4 and CJ-4 are heavy-duty diesel engine-oil categories. They overlap in the market and are often compared, but they were developed for different engine, fuel and after-treatment conditions.
This comparison explains the general differences. Always confirm the exact requirement in the equipment manual and the product TDS; an API category alone does not prove suitability for a specific engine.
At a glance
| Category | Typical focus | Soot control | Fuel / after-treatment | Before ordering |
|---|---|---|---|---|
| API CH-4 | Older heavy-duty diesel engines | Good for its period | Typically older engines; check fuel sulfur | Confirm the manual and OEM approval |
| API CI-4 | Cooled EGR and higher soot loading | Improved soot and viscosity control | Often older after-treatment; check fuel | Confirm the manual and OEM approval |
| API CJ-4 | Low-sulfur fuel and advanced after-treatment | Strong soot control with ash limits | DPF/SCR; low-sulfur fuel | Check ash, phosphorus and OEM approval |
What the letters mean
The API C series covers diesel engine service. CH-4, CI-4 and CJ-4 are successive categories, but the newest one is not a universal upgrade. Each was introduced to address the engines, fuels and emission systems of its time.
Why CJ-4 is not automatically better
CJ-4 was developed around low-sulfur fuel and advanced after-treatment, with limits on ash, phosphorus and sulfur. An older engine that specifies CI-4 may not be approved for CJ-4, and high-sulfur fuel can affect the result. Check the OEM approval rather than assuming that a newer category is safer.
What to check before ordering
Confirm the engine model, model year, emission system, fuel sulfur level and the exact OEM requirement. Ask for the current TDS and evidence of the approval for the product you will receive. Keep different engine requirements on separate order lines.
Bottom line
Start with the OEM requirement. If the manual specifies CI-4, confirm in writing whether CJ-4 is approved before switching.