API CH-4 vs CI-4 Diesel Engine Oil: Which Does Your Fleet Need?

By the Lubesouq technical team · Last updated: 5 July 2026

API CI-4 replaces CH-4 in every application. CI-4 was built for EGR engines and handles more soot and acid than CH-4, and API confirms it can be used wherever CH-4 is specified. If your fleet mixes old and new trucks, one CI-4 oil covers both. Simple as that.

What API CH-4 means

API CH-4 was introduced in 1998 for high-speed four-stroke diesel engines built to meet the 1998 US EPA emission standards. It is formulated for diesel fuel with up to 0.5% sulfur — which matters in markets where higher-sulfur diesel is still in circulation.

CH-4 itself superseded the older CD, CE, CF-4, and CG-4 categories. It set the baseline for wear control, high-temperature stability, and soot handling that modern fleet oils build on.

What API CI-4 means

API CI-4, licensed from 2002, was the first oil category designed for engines using cooled exhaust gas recirculation (EGR). EGR routes exhaust — with its acids and soot — back through the engine, and the oil has to absorb that punishment.

Compared with CH-4, CI-4 oils deliver better soot dispersancy, better control of corrosive and soot-related wear on rings, liners and bearings, better oxidation resistance, and stronger acid neutralization (TBN retention). Qualification added two cooled-EGR engine tests: the Mack T-10 and the Cummins M11 EGR. Per the SAE paper that introduced the category, CI-4 oils were qualified at soot loads of 6–9% — levels no earlier category had to survive.

CI-4 PLUS (2004) is a supplemental designation on top of CI-4, adding resistance to soot-related thickening and better shear stability.

Backward compatibility: the API position

API's official wording: CI-4 oils "can be used in place of CD, CE, CF-4, CG-4, and CH-4 oils." The reverse is not true — a CH-4 oil should not go into an EGR engine that specifies CI-4.

Manufacturer datasheets reflect this. Shell Rimula R4 15W-40, for example, carries API CI-4 PLUS, CI-4, CH-4, CG-4, CF-4 and CF on one label — one oil legitimately covering the whole legacy stack. That is why mixed-age fleets consolidate on a CI-4 oil.

CH-4 vs CI-4 at a glance
	API CH-4	API CI-4
Introduced	1998	2002
Designed for	1998 EPA emission engines (pre-EGR)	2002–2004 EPA engines with cooled EGR
Max fuel sulfur	0.5%	0.5%
Soot handling	Baseline for its era	Upgraded dispersancy; tested at 6–9% soot (Mack T-10, Cummins M11 EGR)
Replaces	CD, CE, CF-4, CG-4	CD, CE, CF-4, CG-4 and CH-4
Status (July 2026)	Current, licensable API category	Current, licensable API category

What comes after CI-4

Newer API categories exist: CJ-4 (2006, for engines with diesel particulate filters), and CK-4 and FA-4 (2016–2017). CK-4 is backward compatible with CI-4 and CH-4; FA-4 is not — API states it plainly. CJ-4 and CK-4 assume low-sulfur fuel, which is why CH-4 and CI-4 — both tolerant of 0.5% sulfur fuel — remain current, licensed categories and remain the right choice for much of the regional fleet and equipment population.

The next generation (PC-12: API CL-4 and FB-4) has a first license date of 1 January 2027. As of this guide's date, no CL-4 oil is on the market — treat any "CL-4" label you see before 2027 with suspicion.

CI-4 replaces CH-4 and everything before it. FA-4 (2016) is the one category that is NOT backward compatible.

15W-40 or 20W-50 in UAE heat?

The second number in an SAE grade is the oil's viscosity at operating temperature. 15W-40 is the default heavy-duty grade worldwide and the standard grade on the major CI-4 lines. 20W-50 holds a thicker film at sustained high temperatures — Chevron's guidance is that 20W-50 "is typically reserved for high temperature conditions." In practice, Gulf operators run 20W-50 in older, high-hour engines working through summer, and 15W-40 in everything else.

If the OEM manual specifies a grade, follow it. Drain intervals are OEM-set too — a premium CI-4 oil supports the OEM-maximum interval, not a magic extension beyond it.

CH-4 and CI-4 oils in stock at Lubesouq

Every product below is live and in stock — prices in AED on the product page.

Frequently asked questions

Can I use CI-4 oil in an engine that asks for CH-4?+

Yes. API states CI-4 oils can be used in place of CH-4 (and CD, CE, CF-4, CG-4). CI-4 meets everything CH-4 requires and adds EGR-grade soot and acid control.

Can I use CH-4 oil in an engine that specifies CI-4?+

No. CI-4 exists because CH-4 oils could not reliably protect cooled-EGR engines from the extra acid, soot, and oxidation. Downgrading risks ring, liner, and bearing wear.

Are CH-4 and CI-4 obsolete now that CK-4 exists?+

No. As of July 2026 both are still current, licensable API categories. They also tolerate diesel with up to 0.5% sulfur, which the newer CJ-4/CK-4 categories — built around low-sulfur fuel — do not assume.

Should I run 15W-40 or 20W-50 in the UAE?+

Follow the OEM manual first. 15W-40 is the standard heavy-duty grade. 20W-50 is typically reserved for sustained high-temperature service — commonly older, high-hour engines working through Gulf summers.

Does CI-4 let me extend drain intervals?+

Drain intervals are set by the engine OEM, not the oil category. A quality CI-4 or CI-4 PLUS oil supports the OEM-maximum interval. We don't promise more than that, and you should be wary of anyone who does.

Sources

Facts in this guide were cross-checked against the following on 5 July 2026:

Not sure which grade fits your equipment? Message us on WhatsApp — +971 50 296 5485 — with the machine model and we'll answer honestly, even if the answer is "you don't need the expensive one."