AMSOIL SIGNATURE SERIES 5W-40 100% SYNTHETIC MAX-DUTY DIESEL OIL

AMSOIL Signature Series 5W-40 100% Synthetic Max-Duty Diesel Oil is a top-tier synthetic diesel oil built to protect hard-working turbodiesel engines in pickups, heavy-duty trucks, and off-road equipment while confidently extending drain intervals well beyond conventional oil capabilities.

Modern diesel engines operate under punishing conditions. High combustion pressures, extreme exhaust gas temperatures, heavy soot loading, and the added stress of towing or performance tuning all conspire to break down lesser oils. Turbodiesel pickups like the Ram 2500 Cummins, Ford F-250 Power Stroke, and GM Duramax run hotter and harder than ever, and the oil has to keep up. Commercial fleets running Detroit Diesel DD13 or DD15 engines, Caterpillar equipment, or Mack powertrains face similar demands at even higher duty cycles.

6X MORE WEAR PROTECTION THAN THE DETROIT DIESEL STANDARD
Ring and cylinder liner wear leads directly to lost compression, reduced horsepower, and increased oil consumption. In third-party testing using the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222, Signature Series Max-Duty delivered 6X more wear protection than required by the standard. Compared to a leading conventional 15W-40, AMSOIL kept cylinder liners looking like new while the competing brand produced severely scuffed liners. That level of protection matters in a Cummins 6.7L pulling a fifth wheel or a fleet DD13 logging 100,000+ miles a year.

UP TO 60% BETTER TURBO CLEANLINESS
Carbon deposits on turbocharger components restrict airflow, reduce boost response, and shorten turbo life. This is especially problematic in trucks that tow heavy loads regularly or run aftermarket tunes pushing higher boost and exhaust gas temperatures. Signature Series 5W-40 delivers up to 60% better turbo cleanliness based on specification standards of the CAT C13 2nd Ring Top Land Carbon test. It withstands the thermal extremes that cause conventional and competing synthetic oils to break down and leave deposits behind.

SUPERIOR VISCOSITY CONTROL AND SOOT MANAGEMENT
Diesel combustion generates soot, and soot causes oil to thicken. Thickened oil flows poorly, starves bearings, and accelerates wear. Signature Series Max-Duty uses top-tier synthetic base oils that naturally resist oxidation and the thickening effects of soot contamination. Boosted detergent and dispersant additives keep soot particles suspended independently, preventing them from agglomerating into larger, wear-causing particles. The oil retains its viscosity after high-temperature service, maintaining proper flow and film strength throughout the drain interval.

UP TO 76% LESS OIL CONSUMPTION
Nobody wants to add a quart between changes. Signature Series 5W-40 has a low rate of volatility (burn-off), reducing oil consumption during operation and passing less oil vapor into the combustion chamber. In the Caterpillar-1N oil consumption test, it delivered up to 76% less oil consumption than required by the API CK-4 standard, consuming just 0.12 g/kWh versus the 0.5 g/kWh CK-4 limit. Less oil consumption means less topping off, less exhaust emissions, and a healthier DPF.

EXTREME-TEMPERATURE PERFORMANCE
The 5W-40 viscosity grade (product code DZF for the 0W-40 variant offers even broader cold-weather range) gives Signature Series DEO a broad operating window. It offers 4X better cold-cranking ability than a 15W-40 oil in the ASTM D5293 cold-cranking viscosity test, staying fluid in sub-zero temperatures for easier starting, improved oil flow at startup, and reduced dry-start wear. Unlike conventional oils, Signature Series contains no wax, so it flows freely in extreme cold. On the hot side, it resists thermal breakdown better than conventional and competing synthetic diesel oils, making it well suited for towing in summer heat or running hard in desert and construction environments.

UP TO 2X BETTER RUST PROTECTION
Engines that sit idle between uses or operate in humid environments are vulnerable to internal corrosion. In industry-standard testing using the NMMA FC-W Rust Test, Signature Series Max-Duty provided up to 2X better rust protection than the pass/fail limit. This is relevant for seasonal equipment, backup generators, and trucks that may sit between jobs.

SPECIFICATIONS AND COMPATIBILITY
Signature Series 5W-40 (DEO) meets or exceeds a wide range of OEM and industry specifications: API CK-4/SN, CJ-4, CI-4+, CF, CF-2, Volvo VDS4.5, VDS4, VDS3, Mack EOS-4.5, EO-O, Renault RLD-4, RLD-3, Cummins CES20086, CES20081, Caterpillar ECF-2, ECF-3, ECF-1-a, DDC 93K218, 93K215, 93K214, DFS 93K222, ACEA E9, E7, MB 228.31, MAN 3575, MAN 3677, MTU Type 2.1, II, I, JASO DH-2, Allison TES439, Deutz DQC III-10LA, Scania LA-2, Chrysler MS 10902, Ford WSS-M2C171-F1, and Deutz DQC IV-10LA. It is compatible with other conventional and synthetic engine oils, though mixing will shorten the oil's life expectancy and reduce its performance benefits. Aftermarket oil additives are not recommended.

SERVICE LIFE
For heavy-duty on-road and off-road diesel applications, Signature Series 5W-40 supports drain intervals up to 3X the OEM recommendation, not to exceed 60,000 miles, 600 hours, or one year, whichever comes first. For turbodiesel pickups, drain intervals up to 2X the OEM recommendation are supported, not to exceed 25,000 miles or one year. Gasoline engine applications support 2X OEM intervals up to 15,000 miles or one year. Extended drain intervals are not recommended for performance-modified engines or when using biofuels containing more than 10% ethanol or 15% biodiesel (B15). Drain intervals may be extended further with oil analysis.