AMSOIL 15W-40 HEAVY-DUTY DIESEL AND MARINE OIL

AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil is a premium synthetic 15W-40 diesel oil built for engines that work hard and run without exhaust aftertreatment systems. It delivers extended drain capability, aggressive soot control, and acid neutralization in a formulation purpose-built for pre-DPF diesels, marine engines, and heavy equipment.

Diesel engines running EGR systems, burning high-sulfur fuel, or operating under sustained load face a relentless combination of soot loading, acid formation, and thermal stress. Conventional 15W-40 oils break down under these conditions, allowing soot particles to aggregate and acids to attack bearing surfaces and cylinder walls. An oil that can handle the real demands of a working diesel needs to be engineered from the ground up with that abuse in mind.

CONTROLS SOOT THICKENING AND WEAR
Soot is unavoidable in diesel combustion, and EGR-equipped engines generate even more of it. The problem isn't soot itself but what happens when particles clump together into larger, abrasive clusters. These aggregated particles cause cylinder bore polishing, accelerate ring and liner wear, and drive viscosity increases that compromise oil flow. AMSOIL 15W-40 Diesel and Marine Oil is heavily fortified with dispersant and detergent additives that keep soot particles suspended independently, preventing aggregation. The Four-Ball Wear Test (ASTM D4172) result of 0.48 mm scar diameter reflects the formulation's ability to maintain a durable lubricating film even in contaminated oil conditions. This matters in engines like the Cummins 5.9L ISB, Detroit Diesel Series 60, and CAT C-series that are known to load oil with soot quickly under heavy duty cycles.

NEUTRALIZES ACIDS WITH A 12.1 TBN
Combustion byproducts, sulfuric acid from high-sulfur diesel fuel, and blow-by gases constantly attack engine internals. The Total Base Number measures an oil's reserve alkalinity and its capacity to neutralize these acids before they cause corrosion. AMSOIL 15W-40 Diesel and Marine Oil carries a TBN of 12.1, providing substantial acid-neutralizing capacity that supports extended drain intervals and protects against corrosive wear in engines running on both low- and high-sulfur fuels. That high TBN is a key reason this oil is favored in marine diesel applications, where sulfur content in fuel can vary widely and corrosion protection is critical.

REDUCES OIL CONSUMPTION AND EMISSIONS
Volatility is a direct driver of oil consumption. When lighter oil molecules boil off in a hot engine, the oil thickens, consumption increases, and hydrocarbon emissions rise. AMSOIL 15W-40 Diesel and Marine Oil posts a Noack Volatility of just 4.2% weight loss (ASTM D5800), which is significantly lower than most conventional 15W-40 petroleum oils. Less oil vapor enters the combustion chamber, consumption stays low, and the oil retains its viscosity grade through extended service. Owners of pre-DPF trucks like the 2001-2007 Duramax LB7, LLY, and LBZ, or the 5.9L Cummins in Ram 2500 and 3500 trucks, consistently report minimal oil consumption with this product.

PERFORMS IN TEMPERATURE EXTREMES
Cold-cranking viscosity at -20°C measures 5,173 cP (ASTM D5293), and the pour point reaches -38°C (-36°F). That means faster oil flow at startup in cold climates, reducing the dry-start wear that does the most cumulative damage to bearings and cam followers. On the high-temperature side, the High-Temperature/High-Shear viscosity of 4.3 cP (ASTM D5481) confirms the oil maintains a protective film under the most severe operating temperatures and loads. The viscosity index of 143 reflects a formulation that remains stable across a wide temperature range, from sub-zero mornings to sustained full-load hauling in summer heat.

BUILT FOR EXTENDED DRAIN INTERVALS
The synthetic base oils and long-drain additive package in AMSOIL 15W-40 Diesel and Marine Oil support drain intervals well beyond conventional petroleum oil limits. In diesel engine service, it is rated for three times the OEM-recommended interval, not to exceed 50,000 miles, 600 hours, or one year, whichever comes first. In gasoline engine applications, it supports two times the OEM interval, not to exceed 15,000 miles or one year. Drain intervals can be extended further with oil analysis. Extended drain intervals are not recommended when using biofuels containing more than 10% ethanol or 10% biodiesel (B10).

Specifications and Compatibility
AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil meets or exceeds the following specifications: API CI-4+, CI-4, CH-4, CF, CF-2, SL, SJ; ACEA A3/B3, E2, E3, E5, E7; Global DHD-1; JASO DH-1; Mack EO-M, EO-N; Caterpillar ECF-1A, ECF-2; Cummins CES 20076, 20077, 20078; Volvo VDS-2, VDS-3; Mercedes-Benz 228.1, 228.3, 229.1; MAN 271, 3275; MTU Type II; DDC 93K214.

This oil is not intended for engines equipped with diesel particulate filters (DPF) or selective catalytic reduction (SCR) systems. Its higher ash content is designed for pre-emissions-era engines and will damage aftertreatment components. For DPF-equipped engines, use an API CK-4 rated product.

It is compatible with conventional and synthetic motor oils, though mixing will shorten the oil's life expectancy and reduce performance benefits. AMSOIL does not support extended drain intervals where oils have been mixed. Aftermarket oil additives are not recommended.

Applications
Engineered for over-the-road trucks, off-road construction equipment, marine diesel engines, farm equipment, mining applications, industrial pumps and generators, and personal vehicles. Commonly used in pre-DPF Duramax trucks (LB7, LLY, LBZ), 5.9L and earlier 6.7L Cummins, 7.3L and 6.0L Power Stroke, Detroit Diesel Series 60, CAT C7 and C15, and a wide range of marine diesel propulsion and auxiliary engines.

Property	Value	Test Method
Kinematic Viscosity @ 100°C, cSt	15.4	ASTM D445
Kinematic Viscosity @ 40°C, cSt	112.9	ASTM D445
Viscosity Index	143	ASTM D2270
CCS Viscosity @ -20°C, cP	5,173	ASTM D5293
Pour Point, °C (°F)	-38 (-36)	ASTM D97
Four-Ball Wear Test, Scar, mm	0.48	ASTM D4172
Noack Volatility, % weight loss	4.2	ASTM D5800
High-Temperature/High-Shear Viscosity, cP	4.3	ASTM D5481
Total Base Number	12.1	—