AMSOIL Signature Series 0W-40 100% Synthetic Max-Duty Diesel Oil
Developed to protect the horsepower diesel enthusiasts crave and extend the life of hard-working commercial equipment in the most severe conditions. Signature Series synthetic technology delivers max-duty protection in on- and off-road applications.
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Product data sheets
View, download, or save a copy of the Product Data Sheet or Safety Data Sheet for AMSOIL Signature Series 0W-40 100% Synthetic Max-Duty Diesel Oil.
AMSOIL Signature Series 0W-40 100% Synthetic Max-Duty Diesel Oil
AMSOIL Signature Series 0W-40 100% Synthetic Max-Duty Diesel Oil is the cold-weather grade of the Signature Series Max-Duty diesel line, formulated for severe-cold starting without giving up CK-4 heavy-duty performance. The 0W-40 grade is built for fleets, work trucks, agricultural and construction equipment, and tuned diesels that face Alaska, Canadian Prairie, Northern Plains, and mountain winters.
Cold-start flow that beats a 15W-40
The 0W-40 grade reaches a CCS viscosity of 5,776 cP at -35 C (ASTM D5293) and a pour point of -48 C / -54 F (ASTM D97), the deepest in the family. The broad 0W to 40 viscosity range delivers 4X better cold-cranking ability than a 15W-40 oil in the ASTM D5293 Cold Cranking Viscosity test, for faster cranking and reduced cold-start wear. Unlike conventional diesel oils, the formula contains no wax and stays fluid in sub-zero temperatures.
Wear protection in heavy-duty service
Wear on rings and cylinder liners drives oil consumption up and pulls horsepower and fuel economy down. Signature Series Max-Duty delivers 6X more wear protection than required by the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222, based on third-party testing using 5W-30 as worst-case representation. In comparison testing against a leading conventional 15W-40 in the same DD13 protocol, Signature Series Max-Duty kept cylinder liners looking like new. The 0W-40 grade records a Four-Ball Wear Test scar of 0.47 mm (ASTM D4172) and an HTHS viscosity of 4.2 cP (ASTM D5481).
Turbo cleanliness for heavy loads and tunes
Turbocharged diesels punish the oil at the bearing and ring belt, especially when towing or running aggressive tunes. Signature Series Max-Duty delivers up to 60 percent better turbo cleanliness, based on specification standards of the CAT C13 2nd Ring Top Land Carbon test, and is built to withstand the extra demand placed on the turbo when the truck is pulling a load or running a horsepower tune.
Soot control and viscosity stability
Top-tier synthetic base oils resist oxidation and soot-related thickening, and boosted detergent and dispersant additives keep soot particles suspended and independent, less likely to agglomerate into wear-causing particles that grind on liners, lifters, and rings. The 0W-40 grade carries a kinematic viscosity of 15.7 cSt at 100 C and 92.8 cSt at 40 C (ASTM D445), with a viscosity index of 180 that holds working viscosity from sub-zero starts through hot, loaded operation.
Reduced oil consumption and rust protection
Lower volatility means less evaporative oil consumption, and Signature Series Max-Duty delivers up to 76 percent less oil consumption than required by the API CK-4 standard in the Caterpillar 1N oil consumption test. The same formula provides up to 2X better rust protection in the NMMA FC-W rust test, important for equipment that sits seasonally or operates in humid or salted-road environments.
Recommended applications and service guidance
Use the live AMSOIL product page and your owner's manual to confirm the current viscosity, API category, OEM approvals, and service guidance for your engine before ordering. AMSOIL updates approvals and recommendations as formulas and manufacturer requirements change.
For extended service, follow the current AMSOIL guidance, your equipment manual, and oil-analysis results. Extended intervals are not appropriate for every engine or operating condition, especially modified engines, unusual fuels, racing use, or equipment with special service restrictions.
Typical technical properties
Property
Value
Kinematic Viscosity at 100 C, cSt (ASTM D445)
15.7
Kinematic Viscosity at 40 C, cSt (ASTM D445)
92.8
Viscosity Index (ASTM D2270)
180
CCS Viscosity, cP at -35 C (ASTM D5293)
5,776
Pour Point, C (ASTM D97)
-48
Four-Ball Wear Test scar, mm (ASTM D4172)
0.47
NOACK Volatility, percent weight loss (ASTM D5800)
Signature Series 0W-40 Max-Duty Diesel Oil is available in quart bottle (DZFQT-EA), case of 12 quarts (DZFQT-CA), gallon jug (DZF1G-EA), and 55 gallon drum (DZF55-EA) sizes. Using AMSOIL synthetic lubricants and practicing extended drain intervals does not void a new vehicle or equipment manufacturer warranty, and all AMSOIL lubricants and filters are covered by the AMSOIL Limited Warranty. Match the right diesel grade and OEM approval set with the AMSOIL Diesel Oil Guide, match the right product in the AMSOIL Vehicle Lookup Guide, then order AMSOIL Signature Series 0W-40 100% Synthetic Max-Duty Diesel Oil.
sticking to what works and what has been used in the truck before me
By David from iowa on July 20, 2026.
Would recommend this to a friend.
6.7 Powerstroke
I have been using this exclusively in my 2016 F350. It out performs the Motorcraft Oil by a large margin. I drive lots of short trips. The Florida temps in Spring, Summer and Fall are routinely above 90°F. The severe service schedule suits me for my driving style.
By Robert from St Augustine, Florida on July 16, 2026.
Would recommend this to a friend.
Click no more
I have always had a feint clicking from my Diesel. Put Amsoil in for the first time and no more clicking (knocking)
What makes 0W-40 different from 15W-40 or 5W-40 Max-Duty?
The 0W-40 grade is the cold-weather member of the Signature Series Max-Duty diesel family. It carries the deepest pour point at -48 C (-54 F), the highest viscosity index at 180, and the lowest CCS cold-cranking viscosity in the line, measured at -35 C. That broad viscosity range delivers 4X better cold-cranking ability than a 15W-40 oil in the ASTM D5293 Cold Cranking Viscosity test, while still meeting API CK-4 at operating temperature. For warm climates or steady on-highway use, the 5W-40 (DEO) or 15W-40 (DME) grades may be the better fit.
Is 0W-40 too thin for a heavy-duty diesel engine?
The first number describes cold-flow performance and the second number describes hot-temperature viscosity. At 100 C, Signature Series 0W-40 measures 15.7 cSt with an HTHS viscosity of 4.2 cP (ASTM D5481), placing the working viscosity in the heavy-duty range. The 0W rating only changes how the oil flows during cold starts. Match the engine manufacturer specification before substituting one viscosity for another.
How do I confirm current approvals?
Confirm the current API category, OEM approvals, and viscosity guidance on the live AMSOIL product page before service. Approval lists can change when formulas or manufacturer requirements are updated.
How long can the oil stay in service?
Use the current AMSOIL product guidance, your owner's manual, and oil-analysis results to set the service interval. Extended service depends on the engine, operating conditions, fuel, filtration, and maintenance history.
Can Signature Series 0W-40 be mixed with conventional or other synthetic diesel oils?
The formula is compatible with other conventional and synthetic engine oils, but mixing shortens oil life and reduces performance benefits. Extended drain intervals are not supported when oils have been mixed, and aftermarket oil additives are not recommended for use with AMSOIL synthetic diesel oils.
Will running Signature Series 0W-40 void a new diesel engine warranty?
No. Using AMSOIL synthetic lubricants and practicing extended drain intervals does not void a new vehicle or equipment manufacturer warranty, and all AMSOIL lubricants and filters are covered by the AMSOIL Limited Warranty.
