Best Diesel Engine Oil
for Semi Trucks
Looking for the best diesel engine oil for semi trucks? AMSOIL Signature Series Max-Duty 15W-40 (DME) is our top choice where its viscosity and approvals match the engine. It delivers 6X more wear protection than required by the Detroit Diesel DD13 Scuffing Test. In eligible heavy-duty on-/off-road diesel service, its published service life is three times the OEM recommendation, not to exceed 60,000 miles, 600 hours or one year—whichever comes first. Restrictions apply.
Top Picks
Max-Duty
AMSOIL Signature Series Max-Duty 15W-40
Top-tier full synthetic engineered to provide maximum engine life under extreme high-temperature operating loads. Delivers up to 76% less oil burn-off than standard API CK-4 criteria require.
- Cummins CES 20086 Approved
- Detroit Diesel DFS 93K222 Approved
- Volvo VDS-4.5 / Mack EOS-4.5 Approved
- 6X more wear protection vs test mandates
- Up to 60% better turbo cleanliness
- Allison TES-439 Approved
AMSOIL Signature Series 5W-30
- Outperforms conventional 15W-40 in Detroit DD13 scuffing test*
- 76% less oil consumption vs API CK-4 standard*
- Works in diesels, gas trucks, farm equipment, and marine
- Meets API CK-4, Detroit DFS 93K222, Cummins, Volvo, Mack
- 2× OEM recommendation for turbodiesel pickups*
Heavy-Duty
AMSOIL Heavy-Duty 100% Synthetic
- 4× wear protection vs Detroit Diesel DD13 Scuffing Test spec*
- 66% less oil consumption vs API CK-4 standard (Cat-1N test)*
- Wide OEM approval: Volvo VDS-4.5, Mack EOS-4.5, Cummins, CAT, Detroit, Allison TES, MB, MAN, MTU
- Service life: OEM drain interval (extendable with oil analysis)
- Full synthetic at a step below Signature Series pricing
AMSOIL Heavy-Duty Diesel & Marine
- TBN 12 — highest acid neutralization in the AMSOIL diesel lineup
- Controls soot thickening from EGR blow-by in older engines
- 3× OEM drain interval for diesel service*
- Excellent for marine diesels, farm equipment, off-road, and pre-2007 on-highway engines
- ⚠ Not for use in engines with DPF or SCR aftertreatment
Commercial Grade
AMSOIL Commercial Grade
- 50%+ synthetic content — well above competitors at this price
- 2× wear protection vs Detroit Diesel DD13 Scuffing Test spec*
- Meets API CK-4, CJ-4, CI-4+, Volvo VDS-3, Mack EO-O, Cummins, CAT, Detroit
- Service life: OEM drain interval (extendable with oil analysis)
- Best entry point for fleets moving up from conventional oil
API Specs: CK-4 vs FA-4
Both performance categories handle modern emissions requirements, but their distinct film properties limit interchangeability.
| Feature | CK-4 | FA-4 |
|---|---|---|
| HTHS Viscosity Limits | ≥ 3.5 mPa·s (Robust oil film) | 2.9–3.2 mPa·s (Lower drag target) |
| Fuel Economy Advantage | Standard baseline | Measurable fuel reduction |
| Backward Compatibility | Yes — replaces CJ-4, CI-4+, legacy specs | No — restricted to cleared platforms only |
| Primary Freight Application | Broad Class 8 use | Select newer fuel-efficient engines |
| Legacy Equipment Safety | Yes | No — may accelerate bearing scuffing |
| Mixed Fleet Selection | Yes | Only when owner's manual explicitly lists FA-4 |
Full breakdown: CK-4 vs FA-4 | Which Diesel Oil Spec Does Your Engine Actually Need →
Viscosity Grades for Semi Trucks
15W-40 is the baseline across most Class 8 applications. Cold climate operations and specific OEM approvals may call for a different grade.
Global baseline for long-haul operations. Retains thermal protection across varying loads.
Improves pumpability in lower operating ranges. Reduces cold-start wear risk.
Maximum cold-flow in extreme cold zones. 0W-40 offers 4X better cold-cranking than 15W-40 in ASTM D5293 testing.
Applied in specific legacy or vocational applications where OEM guidance calls for it.
Viscosity by temperature and engine: Semi Truck Oil Weight Chart →
Choosing Oil by Duty Cycle
The same engine can have different oil requirements depending on how it's being used. Long-haul highway miles are the friendliest environment for extended drain programs. Vocational and urban operation are not.
Sustained highway RPM, stable oil temperature and fewer cold-start cycles per operating hour can make line-haul service suitable for a managed extended-drain program.
Where DME 15W-40 matches the engine specification, follow its product-specific limit: three times the OEM recommendation, not to exceed 60,000 miles, 600 hours or one year. Use oil analysis to monitor actual lubricant condition.
Cummins X15 engine oil →Dump trucks, cement mixers, refuse, logging, oilfield. Frequent cold starts, high idle, extreme load cycling, and contaminant ingestion shorten oil life significantly. Extended drains are not the right call here.
ADP 15W-40 meets EOS-4.5 for Mack heavy vocational. Protection under extreme stress is the priority over drain interval length.
Mack MP8 engine oil →Short haul, frequent stops, engine-off cycles. Cold-start wear events accumulate faster than in line-haul. Fuel dilution is a real risk. Oil analysis is still useful here, but the economics of extending drains past 2X OEM are weaker.
Follow the engine manufacturer's duty-cycle classification and use oil analysis to establish whether any extension is appropriate.
Volvo D13 engine oil →By Engine | OEM Oil Specs
API CK-4 is the floor. Every major OEM runs its own proprietary validation on top of that. Your oil needs to pass both.
Strict limits on thermal breakdown, valvetrain fatigue, and soot accumulation. Both DME and ADP approved.
Cummins X15 Engine Oil →Detroit's scuffing wear defense specification. Fully certified by both DME and ADP.
Detroit Engine Oil →Strict shear thinning and oxidation limits under heavy long-haul cycles. Fully certified.
Volvo D13 Engine Oil →Mack's flagship heavy transport protocol. Approved across both AMSOIL product lines.
Mack MP8 Engine Oil →Confirm the exact PACCAR lubricant specification and viscosity using the engine model, build date and current operator's manual.
PACCAR MX-13 Engine Oil →Meets performance criteria for International line-haul engine architecture.
International LT Engine Oil →One oil may cover several engines in a mixed fleet. Confirm every required approval and viscosity before standardizing on DME 15W-40.
See DME Pricing →Drain Intervals | OEM vs Extended
Oil type alone does not set the drain interval. Use the exact lubricant's published service life, the engine manufacturer's schedule, duty cycle and oil condition. A generic CK-4 or full-synthetic label does not authorize a fixed extended interval.
| Oil or program | Published direction | Maximum / control |
|---|---|---|
| AMSOIL Signature Series Max-Duty | Heavy-duty on-/off-road diesel service: 3× OEM recommendation* | Not to exceed 60,000 miles, 600 hours or one year—whichever comes first* |
| AMSOIL Heavy-Duty 100% Synthetic | Follow the engine manufacturer's drain interval | Extend only through a documented oil-analysis program |
| Other CK-4 synthetic oils | Follow the oil supplier and engine manufacturer | No universal synthetic-oil mileage |
| Vocational / severe duty | Follow the applicable OEM severe-service schedule | Idling, soot, fuel dilution and contamination can shorten service life |
*Restrictions apply. Refer to the current AMSOIL Signature Series Max-Duty product data sheet and the engine manufacturer's recommendations. Oil analysis monitors condition but does not cancel published mileage, hour or time limits.
Oil Analysis for Semi Trucks | How to Extend Drain Intervals Safely →
AMSOIL vs. The Competition
Every oil below carries a CK-4 stamp. The specification sets a floor — it doesn't define the ceiling. These figures are from published manufacturer technical data sheets and third-party test results.
| Oil | Type | HTHS (mPa·s) | 4-Ball Wear (mm) | Noack % | TBN | Allison TES-439 | Extended Drain |
|---|---|---|---|---|---|---|---|
| AMSOIL DME 15W-40 | Full Synthetic | 4.3 | 0.36 | 3.7% | 10.0 | ✓ | 3× OEM; 60K mi/600 hr/1 yr max* |
| AMSOIL ADP 15W-40 | Full Synthetic | 4.3 | 0.36 | 3.7% | 10.0 | ✓ | OEM interval |
| Shell Rotella T6 15W-40 | Full Synthetic | 4.0 | 0.48 | 4.4% | 9.0 | — | OEM interval |
| Mobil Delvac 1 ESP 5W-40 | Full Synthetic | 3.7 | 0.47 | 3.1% | 9.0 | — | OEM interval |
| Chevron Delo 400 XSP 15W-40 | Full Synthetic | 4.0 | 0.44 | 4.1% | 10.0 | — | OEM interval |
| Valvoline Premium Blue Extreme 15W-40 | Full Synthetic | 3.9 | 0.45 | 4.3% | 9.5 | — | OEM interval |
| Castrol Vecton 15W-40 | Full Synthetic | 4.1 | 0.46 | 4.2% | 9.5 | — | OEM interval |
Four-Ball Wear and HTHS data from published manufacturer technical data sheets. Lower wear scar = better protection. Higher TBN = more acid-neutralizing reserve. CK-4 minimum HTHS is 3.5 mPa·s.
Best Diesel Engine Oil For Semi Trucks
Frequently Asked Questions
Ready to Switch?
AMSOIL synthetic diesel engine oils deliver long-term wear protection, minimize oil burn-off, and lower total fleet maintenance cost per mile.