What Type of Oil Does a Diesel Truck Need?

A truck needs diesel engine oil that meets the API category, manufacturer approval, and viscosity specified for its engine. For many modern trucks the basis will be API CK-4; certain newer engines may use FA-4. Others also require Volvo VDS, Mack EOS, Cummins CES, Detroit Diesel, MB, MAN, or another standard.

What does the label information mean?

Item	What it answers
API CK-4/FA-4	Diesel service level
ACEA E7/E8/E11	European heavy-duty performance
SAE 15W-40/10W-30/5W-40/5W-30	Cold- and hot-temperature viscosity
OEM approval	Engine-specific requirement
Synthetic/blend	Formulation description, not compatibility

Every mandatory requirement must match.

When is CK-4 used?

API describes CK-4 for four-stroke diesel engines meeting 2017 on-highway and Tier 4 off-highway emissions standards, as well as many earlier engines. CK-4 exceeds several previous categories.¹

When is FA-4 used?

FA-4 applies to certain lower-HTHS XW-30 oils for selected engines. It is neither interchangeable with nor backward-compatible with CK-4.¹

Which viscosity is correct?

The manual defines the range. 15W-40 is common, but 10W-30 and synthetic 5W grades may be required or permitted. Do not decide only by age or climate.

Which options does Inforca document?

The active portfolio includes MANNOL TS-14 15W-40, TS-17 5W-30, TS-16 5W-40, TS-18 15W-40, and PureGuard PG206 15W-40, all positioned as CK-4 in available materials.²

The current portfolio does not verify a FA-4 SKU. Confirm whether that category is needed before quoting.

Synthetic or blend?

A synthetic may improve low-temperature and oxidation properties, but it does not replace an approval. Compare results and total cost through a pilot.

What about an older engine?

CK-4 can cover many earlier categories, but two-stroke engines, monogrades, high-sulfur fuel, or special designs require review. API warns that diesel backward compatibility is not always universal.¹

Frequently asked questions

Do all trucks use 15W-40?

No.

Can gasoline oil be used in a diesel?

Only if it also claims the required diesel category.

Is FA-4 better than CK-4?

No; it is different and restricted to approved engines.

Can you change brands?

Yes, when the alternative covers every standard and the transition is controlled.

Does a DPF require special oil?

It requires the compatible category and approval stated by the manufacturer.

Confirm the engine before buying

Send Inforca the engine, series, year, API/ACEA/OEM requirement, viscosity, DPF/SCR, fuel, duty cycle, capacity, volume, and presentation.

Sources

Footnotes

1. American Petroleum Institute, Oil Categories, accessed September 10, 2026. ↩ ↩² ↩³

2. Inforca International, Engine Oils, accessed September 10, 2026. ↩