
Buy 5 Quarts - GET FREE SHIPPING - Promo code: FIVE221
Exclusive offer for Online and Preferred Customers
Signature Series Max-Duty Synthetic Diesel Oil 5W-40
Product code : DEOQT-EA
• Outstanding extreme-pressure protection
• Delivers 6X more wear protection1
• Maintains proper viscosity (thickness)
• Minimizes oil consumption
• Maximizes fuel efficiency
• Excels in extreme temperatures
1Based on third-party testing in the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222 using 5W-30 as worst-case representation
• Outstanding extreme-pressure protection
• Delivers 6X more wear protection1
• Maintains proper viscosity (thickness)
• Minimizes oil consumption
• Maximizes fuel efficiency
• Excels in extreme temperatures
1Based on third-party testing in the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222 using 5W-30 as worst-case representation
Signature Series Max-Duty Synthetic Diesel Oil 5W-40
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.
See the Product Data Bulletin for full details.
MAXIMUM ENGINE PROTECTION
- Delivers 6X more wear protection,1 delivering extra protection so you can push your diesel with peace of mind
- Provides long-lasting wear protection, keeping cylinder liners looking like new2
- Delivers up to 60 percent better turbo cleanliness3
- Withstands the extra demands you place on the turbo when pulling heavy loads or updating the tune for maximum horsepower
- Provides up to 2X better rust protection4
1Based on third-party testing in the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222 using 5W-30 as worst-case representation
2Based on independent testing of AMSOIL 5W-30 Signature Series Max-Duty Synthetic Diesel Oil and a leading conventional 15W-40 diesel oil using the Detroit Diesel* DD13 Scuffing test for specification DFS 93K222.
3Based on specification standards of CAT C13 2nd Ring Top Land Carbon testing
4Based on industry standard testing using the NMMA FC-W Rust Test.
Delivers More Wear Protection
Third-party testing shows Signature Series Max-Duty Synthetic Diesel Oil delivers 6X more protection against wear than required by Detroit Diesel’s* standard.II
IIBased on third-party testing in the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222 using 5W-30 as worst-case representation.
*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use.
AMSOIL Fights Wear
AMSOIL delivers powerful engine protection. How good is it? In third-party testing compared to a leading brand, AMSOIL provided long-lasting wear protection, keeping cylinder liners looking like new.DD

DDBased on third-party testing of AMSOIL 5W-30 Signature Series Max-Duty Synthetic Diesel Oil and a leading conventional 15W-40 diesel oil using the Detroit Diesel* DD13 Scuffing test for specification DFS 93K222.
*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use.
Keeps Turbos Clean
AMSOIL Signature Series Max-Duty Synthetic Diesel Oil provides protection boosted to the max, delivering up to 60% better turbo cleanlinessJ and withstanding the extra demands you place on the turbo when pulling heavy loads or updating the tune for maximum horsepower.
JBased on specification standards of CAT C13 2nd Ring Top Land Carbon testing
Protects Against Rust
Provides up to 2X better rust protection.K
KBased on industry standard testing using the NMMA FC-W Rust Test.
VISCOSITY CONTROL
- Resists oxidation and the thickening effects of soot contamination
- Retains viscosity after high-temperature service for maximum engine protection and efficiency
- Provides up to 76 percent less oil consumption5
5Than required by the API CK-4 standard in the Caterpillar-1N oil consumption test
Reduces Oil Consumption
Signature Series Max-Duty Synthetic Diesel Oil provides up to 76% less oil consumption.L

LThan required by the API CK-4 standard in the Caterpillar-1N oil consumption test.
EXCELS IN EXTREME TEMPERATURES
- Provides outstanding protection and performance in hot and cold temperature extremes
- Resists thermal (heat) breakdown better than conventional and competing synthetic diesel oils.
- Stays fluid in sub-zero temperatures for easier starting, improved oil flow and reduced wear.
Signature Series Max-Duty Synthetic Diesel Oil 5W-40
SDS
Download the SDS
Data Bulletins
Download the Data Bulletins
WARRANTY
Download the WARRANTY
Signature Series Max-Duty Synthetic Diesel Oil 5W-40
-
Diesel oilLove amsoil the only oil I run in my diesel truckBottom LineYes, I would recommend this to a friend.
-
Bottom LineYes, I would recommend this to a friend.
-
Bottom LineYes, I would recommend this to a friend.
-
Difference you can hereI was running another big name brand (T6) synthetic oil before, after switching to AMS oil I can here a difference in how the motor idles. Much smoother and quieter than beforeBottom LineYes, I would recommend this to a friend.
-
Best oilNot much to say other then best oil on the market. I don’t use anything else. I use this in my 2001 Chevy Duramax that is always towing. 10/10 recommendBottom LineYes, I would recommend this to a friend.
-
GREAT PRODUCT / CUSTOMER SERVICEBy  JAMES,  a  Verified Buyer  from  NORTH CAROLINA  on  February 21, 2021GREAT PRODUCT BEEN USING FOR YEARS WITH NO ISSUES, CUSTOMER SERVICE ALSO RECEPTIVE TO REQUESTS. I FEEL LIKE I KNOW THEM PERSONALLYBottom LineYes, I would recommend this to a friend.
-
By  MICHAEL,  a  Verified Buyer  from  Syracuse,NY  on  February 19, 2021Bottom LineYes, I would recommend this to a friend.
-
#1I drive my diesel approx 4000 plus miles a week. Amsoil is without a doubt the best full synthetic oil and 2nd to noneBottom LineYes, I would recommend this to a friend.
-
315,000 miI've used this oil for years on my truck Duramax diesel 315,000 And the motors never been opened it's all I have to sayBottom LineYes, I would recommend this to a friend.
-
Bottom LineYes, I would recommend this to a friend.