Skip to Main Content
Close Icon

Main Menu

Begin typing to search, use arrow keys to navigate, Enter to select.
Your order may take longer than normal to arrive, and some products may be unavailable. We are working hard to overcome supply-chain issues and freight-carrier delays. Learn more.

Customer Ratings & Reviews

Signature Series Max-Duty Synthetic Diesel Oil 15W-40

Product code : DMEQT-EA

4.9 star rating Read 847 reviews

Customer Rating

4.9

88% would recommend

  • 5 802
  • 4 34
  • 3 3
  • 2 3
  • 1 5

Signature Series Max-Duty Synthetic Diesel Oil 15W-40

4.9 star rating Based on 847 reviews
  • 5 star rating
    Full Circle
    By  DMAX,  a  Verified Buyer  from  Indiana   on  April 11, 2022
    Failed to verify captcha
    So I first started using Amsoil in 1980. I had a 1979 Chevy K20 4x4 with a 4 speed trans. I had changed all lubricants to Amsoil. I remember how impressed I was when pushing in on the clutch in sub zero weather and the truck not feeling like I just hit the brakes. Fast forward to today. I now have a 2015 Duramax and have been using Rotella T6. Due to supply chain issues T6 is getting hard to find in my area so I thought let’s give Amsoil a try again. So after about 3500 miles I have noticed that the Truck is running around 15 to 20 psi higher oil pressure than with T6. Not sure why just an observation.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Best diesel oil
    By  DAVID,  a  Verified Buyer  from  OK  on  April 09, 2022
    Failed to verify captcha
    Been running this oil in my 2004 Chevy LLY Duramax for over 10 years. 218K miles. Still waiting on the EA052 oil filter
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    My new oil!
    By  DAVID,  a  Verified Buyer  on  April 08, 2022
    Failed to verify captcha
    I now have my favorite oil! I will never be using any other oil then this amazing product..
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Great Product
    By  MICHAEL,  a  Verified Buyer  from  Valley Springs, CA  on  April 07, 2022
    Failed to verify captcha
    Love Amsoil products!! Nothing better in my opinion. I run Amsoil in everything I own!!
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Signature series max duty 15w-40
    By  MAHLON,  a  Verified Buyer  from  Westlake, LA.  on  April 07, 2022
    Failed to verify captcha
    I have used this product exclusively in my 2018 duramax. I have done a couple of used oil analysis as well. This oil is great. Wouldn't use anything else. The customer service is great too!
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Signature Series Max-Duty Synthetic Diesel Oil 15W-40
    By  FRANK,  a  Verified Buyer  from  NW Arkansas  on  April 05, 2022
    Failed to verify captcha
    I have great confidence in this oil. I like the idea of extended (25,000 mls) oil change intervals with twice the protection. I find my oil pressure is 3lbs greater when operating at 2000 RPM than with Shell Rotella 15w40 Diesel Oil. Shell Rotella maybe cheaper by the mile, but it has only half the protection.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Signature series diesel oil
    By  WILLIAM,  a  Verified Buyer  on  April 04, 2022
    Failed to verify captcha
    I run this oil in my Silverado duramax I have. I like the better protection this oil provides.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    First Time User
    By  ROGER,  a  Verified Buyer  from  W.V.  on  April 03, 2022
    Failed to verify captcha
    Order arrived quickly, about two or three days. Just changed the oil everything looks good so far.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Arrived leaking
    By  RICK,  a  Verified Buyer  on  April 03, 2022
    Failed to verify captcha
    Arrived fast, however 1 container was leaking had to transfer to another container. A real mess on my steps
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Great oil
    By  CARLOS,  a  Verified Buyer  from  Texas  on  April 02, 2022
    Failed to verify captcha
    This oil is awesome, it feels completely different from other competitors. I will never again use any other oil in any of my trucks.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Great oil
    By  MICHAEL,  a  Verified Buyer  from  PA  on  March 30, 2022
    Failed to verify captcha
    I have been using Amsoil for over 10 years great product all around. I have 2001 F350 w/7.3 diesel. 249,000 miles. Still get great gas mileage. Fast shipping
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Use the best
    By  ROY,  a  Verified Buyer  from  Maine   on  March 28, 2022
    Failed to verify captcha
    I use Amsoil in all my vehicles. My 2020 Ram 2500 with a 6.7 Cummins Takes 13 qts due to the fact I’m using The Amsoil bypass filter set up. With the rising oil prices i can go twice if not more on an oil change. This stuff is The best.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Diesel motor oil
    By  Glenn,  a  Verified Buyer  from  Charlotte,NC  on  March 26, 2022
    Failed to verify captcha
    This is my first time using Amsoil. I have read great reviews so I’m looking forward to long engine life and great performance on my 2021 Ford F 250 6.7 L diesel truck while using this great product with real life and real world testing.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Immediately lessened engine noise. Ran smoother as well.
    By  RICHARD,  a  Verified Buyer  from  Arizona  on  March 24, 2022
    Failed to verify captcha
    First time using this. Immediate results as far as less noise and smoother running engine!
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    03 Lb7
    By  Mike,  a  Verified Buyer  from  Wisconsin  on  March 22, 2022
    Failed to verify captcha
    I finally pulled the trigger and switched to Amsoil. I've been using 15-40 in both my diesel pickups and I'll have a more in depth review once I change my oil again.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Even though it’s more expensive then most it’s a great oil
    By  GREG,  a  Verified Buyer  from  Oregon   on  March 19, 2022
    Failed to verify captcha
    Great oil for my 2004 Cummins with 200,000 miles keeps the engine running smooth
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    2020- 6.7 Cummins 3'rd Service
    By  GARNET,  a  Verified Buyer  from  So Cal  on  March 14, 2022
    Failed to verify captcha
    Instantly sounding much smoother considering how industrial this engine is as a whole- Much quicker to build oil pressure than the Rotella with 5k on it with an ambient of 7*F- Being in So Cal and having a interesting time finding 5w40 approved engine oil,glad to know you guys have it on the shelf- Have purchased a few 2.5 gallon jugs since-
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    LS MT125
    By  CHRIS,  a  Verified Buyer  from  Kansas  on  March 13, 2022
    Failed to verify captcha
    I have a 25 hp LS tractor that I have used the max duty oil in since new and it’s been great. The tractor seems to run cooler than the factory oil and it gets hot in Kansas during mowing season
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Firs time
    By  DANIEL,  a  Verified Buyer  from  Maiden Nc   on  March 13, 2022
    Failed to verify captcha
    For me to be the first time using Amsoil And rate the product I’ll have to see how looks when I do the oil change again then I can said all good or bad things since I never heard of Amsoil before but l am impressive with some of the challenges they had put against other competitors I hope that Amsoil would be my first and forever oil For all my cars
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5 star rating
    Great product!
    By  Proriderxr ,  a  Verified Buyer  from  Ashland, Ohio  on  March 12, 2022
    Failed to verify captcha
    Great oil, let’s my duramax run cooler than rotela oil and stays clean upto 5,000 miles!
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?