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Customer Ratings & Reviews

Signature Series Max-Duty Synthetic Diesel Oil 5W-40

Product code : DEOQT-EA

4.9 Read 756 reviews

Customer Rating

4.9

88% would recommend

  • 5 716
  • 4 31
  • 3 2
  • 2 3
  • 1 4

Signature Series Max-Duty Synthetic Diesel Oil 5W-40

4.9 Based on 756 reviews
  • 5
    Signature Series Max Duty Diesel Oil 15w-40
    By  BILL,  a  Verified Buyer  from  Canada  on  January 18, 2022

    Describe the issue

    I have a 5.9 cummins ram with a fully built compound turbo set-up and Goerend transmission. The truck makes 800+ HP at the wheels and I drive it quite hard. I have only used and will only use Amsoil products for this build. I am 63 and and have seen and used different products over the decades. It is so nice to now just look at the Amsoil website and order what I need for whatever I am working on. I have always told my sons "oil is cheap, engines are expensive"
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    15W-40 oil
    By  LEONARD,  a  Verified Buyer  on  January 17, 2022

    Describe the issue

    This oil works great and protects my engine. It was easy to order and arrived quickly. Thanks
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5
    Amazing oil
    By  HUSSAIN,  a  Verified Buyer  from  Burleson tx  on  January 16, 2022

    Describe the issue

    I ordered this oil because i saw very good amazing reviews and honestly its one of the best oils I've used in my truck gives great protection and great milage
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Happy long time customer
    By  BRUCE,  a  Verified Buyer  on  January 15, 2022

    Describe the issue

    I've been very happy with the customer service with Amsoil for a long time. Easy ordering, very fast shipping. I use their products in all my vehicles. I also use their products in my offshore boat.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Great 👍
    By  Goose,  a  Verified Buyer  from  British Columbia   on  January 15, 2022

    Describe the issue

    I started using amsoil 3 years ago after lots of research and found it to be the best. I use it for everything on my pickup.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 4
    Greatr
    By  DON,  a  Verified Buyer  from  Iowa  on  January 14, 2022

    Describe the issue

    I've run Amsoil in my 6.6 Duramax in screaming hot and sub zero temps with no issues at all. I intend to continue to use it.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5
    Good oil
    By  JARED,  a  Verified Buyer  on  January 13, 2022

    Describe the issue

    Its a good oil but i was surprised i didnt get any stickers. When i bought it previously i got stickers
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Very fast shipping
    By  Chad,  a  Verified Buyer  from  Utah  on  January 12, 2022

    Describe the issue

    Awesome shipping time!!
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Great Product
    By  BRETT,  a  Verified Buyer  from  Cocoa,FL.  on  January 10, 2022

    Describe the issue

    I have used AMSOIL in my Ford diesel for 15 plus years and still going strong at over 444k miles!
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  • 5
    Best thing on the shelf
    By  JEFF,  a  Verified Buyer  from  Unfortunately California  on  January 09, 2022

    Describe the issue

    This is the only thing I have put in my truck seance I have owned my it.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5
    signature oil
    By  Roger,  a  Verified Buyer  from  Tennessee  on  January 09, 2022

    Describe the issue

    I've just now started using this oil and it seems to be a good oil. Engine sounds great and starts quickly, doesn't use a drop. Hopefully it will stand the test of time.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Great company
    By  Josh,  a  Verified Buyer  from  Louisiana  on  January 09, 2022

    Describe the issue

    I love the reorder feature. Great company and product.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Great transaction with great oil
    By  Charles,  a  Verified Buyer  from  KY  on  January 08, 2022

    Describe the issue

    Quick delivery of great product for awesome price when all others are going crazy on price.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5
    The best oil for l5p
    By  BRIAN,  a  Verified Buyer  from  Florida  on  January 08, 2022

    Describe the issue

    I believe that you should only use one oil for the life of your engine. Since my 2017 gmc Denali 2500 was new My first oil change I started using asm oil I never had warranty repair made on my truck. I am a ase master tech for Cadillac and shop foremen I’ve got my service write To start to using asm oil in his ats v And I use in my ats v too They are the only oil company that has spec On there oil and numerous hours for test I’m a believer yes it maybe a little more money but worth it and if Gale Banks Believe in ams oil that seals the deal with me :).
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Great product!
    By  WILL,  a  Verified Buyer  from  Corpus Christi, TX  on  January 08, 2022

    Describe the issue

    Been using amzoil for almost 15 years in my powerstroke and my cummins. Won't use anything else.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    Diesel oil
    By  BRIAN,  a  Verified Buyer  from  Florida   on  January 08, 2022

    Describe the issue

    My family has used the product in 6.2 Durmax for years.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5
    Best oil for my Duramax
    By  LUIS,  a  Verified Buyer  on  January 08, 2022

    Describe the issue

    I’m really happy with the synthetic oil quality for my Duramax.
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5
    Great product Amsoil
    By  JOHN,  a  Verified Buyer  from  Edmond Oklahoma.  on  January 07, 2022

    Describe the issue

    Great product Amsoil is the only oil that I have used for 18 years.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5
    My truck seems to love this oil!!
    By  MICHAEL,  a  Verified Buyer  from  Socal   on  January 03, 2022

    Describe the issue

    Changed from Rotella T6 to this Amsoil Signature Series. My truck seems to love it!! Seems to be running quieter and nice and smooth. Did my friends truck and the same time with the same results. Both very happy at this point!!
    Bottom Line
    Yes, I would recommend this to a friend.
    Was this review helpful?
  • 5
    The only oil I use in my truck
    By  Dado,  a  Verified Buyer  from  CA  on  January 03, 2022

    Describe the issue

    I use my RAM 2500 cummins for towing up and down the Sierra Nevada in the heat of southern California and in the cold of the mountain. This is the only oil i trust in my engine with all the punishment it takes. Ordering directly from amsoil is fast and easy. I do all my own services so it makes financial sense to spend the money on quality oil and filter. I only needed customer service once and they were very helpful.
    Bottom Line
    Yes, I would recommend this to a friend.
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