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Customer Ratings & Reviews

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

Product code : DEOQT-EA

4.9 star rating Read 866 reviews

Customer Rating

4.9

88% would recommend

  • 5 821
  • 4 34
  • 3 3
  • 2 3
  • 1 5

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

4.9 star rating Based on 866 reviews
  • 5 star rating
    customer for live
    By  BOB,  a  Verified Buyer  from  ontario canada  on  July 01, 2022
    I`m 70 years old was in the auto repair business for 49 years. involved in racing my whole life an currently drag race a challenger hellcat. I decided to forge the bottom end of the motor an could not believe how good everything looked inside the motor. connecting rod bearings look like they just came out of the box. pistons an cylinder walls are perfect. but at the same time not all that surprised . always used amsoil an will continue to do so.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Great oil
    By  GREG,  a  Verified Buyer  on  July 01, 2022
    The engine runs cooler and smoother with this oil. Plus I get 7500 to 9000 miles between changes.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Great oil
    By  MICHAEL,  a  Verified Buyer  from  Wilmington  on  June 30, 2022
    Best on the market.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Saves time
    By  TUCKER,  a  Verified Buyer  from  Maine  on  June 23, 2022
    I run this in all of my diesel equipment (tractor, excavator, ram 5500, generator) and only change once a year regardless of miles/hours. This saves me time and money from having to do multiple changes if running conventional oil. It also seems to have a much higher retention/suspension capacity for contaminants than other oils.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    40 year user
    By  ROD,  a  Verified Buyer  on  June 21, 2022
    Been using for 40 yrs. Best of the Best.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Purebred Synthetic.
    By  SCOTT,  a  Verified Buyer  from  SE USA  on  June 20, 2022
    I am so impressed with the results of the laboratory oil analysis since switching to AMSOIL Signature Synthetic motor oils. AMSOIL is a company with a spine of integrity.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Trust your oil...
    By  William,  a  Verified Buyer  from  California  on  June 18, 2022
    I will always use products I can trust in. Amsoil is at the head of my list! I have created quite a few converts. Autos and trucks are usually the second biggest investment in a person's life so DO NOT trust any old oil. I'll stick to this brand so I won't have something else to worry about.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    top Oil
    By  Saintsrph,  a  Verified Buyer  from  AZ  on  June 16, 2022
    Excellent synthetic oil. Provides excellent wear prodection. Use it in all my vehicles
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Best oil out there
    By  DAVID,  a  Verified Buyer  on  June 13, 2022
    This is by far the best oil out there!! And… don’t have to change it all the time
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Last order
    By  MIKE,  a  Verified Buyer  from  Dallas area  on  June 13, 2022
    My order always arrive quickly and accurate. However, my last order the warehouse forgot to include my WIX oil filter. I called Amsoil and they sent me one the next day. Great customer service. Mike
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  • 5 star rating
    oil
    By  Emery,  a  Verified Buyer  from  COLORADO  on  June 11, 2022
    I believe Max duty 6 has kept my 6.6 duramax running at it best, been using its whole life.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    lubrication
    By  Joan,  a  Verified Buyer  from  Idaho  on  June 09, 2022
    My 2002 Dodge 2500 Has been lubricated with AMSOIL products for about 16 years and over 200,000 miles. I would not use any other product. The 5.9BT has all the power and the running gear is smooth and noise free.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Beat diesel Oil
    By  GIANLUCA,  a  Verified Buyer  from  Toronto, Canada   on  June 08, 2022
    Best engine oil I’ve ever used , great for the eco Diesel engine !
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Fleet
    By  BRANDI,  a  Verified Buyer  from  Usa  on  June 06, 2022
    Run this on all of our diesel trucks great for cold weather starts Trucks run smoother and deliver better power than conventional oils
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Signature series sny diesel oil
    By  Jack,  a  Verified Buyer  from  CA - California  on  June 04, 2022
    since switching over to Amsoil Synthetic 15/40 0il ,oil press is better ,engine runs quieter
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Can’t beat your products
    By  PHILLIP,  a  Verified Buyer  on  June 02, 2022
    Your products are great .I now have my son using them & he does more research than anybody I know
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Nothing but this
    By  ANTHONY,  a  Verified Buyer  from  Suffolk, VA  on  June 01, 2022
    When I found out this was available, I started using it. I need to get the other fluids switched over.
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Very true to it's name, Max Duty
    By  DAN,  a  Verified Buyer  from  Iowa  on  May 30, 2022
    Have used this for many years in my Diesel engines and through all of the improvements in formulation over the years it has been very high quality especially matched with the Amsoil 20 micron filters. And the bypass filtration quality of the 2 micron really extends the life and fuel economy characteristics of this specialized Diesel formula. Fuel economy being most important, and the smooth sound of the engine never varies over many many massive highway miles...
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Great diesel oil compared to OTC oils. Great long life oils.
    By  JOSEPH W,  a  Verified Buyer  from  Rocklin, Ca  on  May 29, 2022
    I've been using Amsoil automotive oils and greases almost 20 years. Personally I have seen proven protection of high load/wear bearing surfaces, cylinders walls, and camshaft lobes, enough to swear off OTC products and I don't run anything else. The slightly higher costs I've paid for Amsoil products are offset by my overall savings in vehicle, motorcycle maintenance, and what I feel based on experience is unusually extended and trouble free vehicle service life since I began using Amsoil products on my personal vehicles and my family's vehicles. My opinion is Amsoil products rate of return begins immediately once it is. Amsoil keeps engines clean which helps protect the motor better. Amsoil does protect internal wear surfaces better than any oil I've compared it to. Testing different oils led me to Amsoil and I haven't turned back since my first purchase, For me OTC oils just don't compare to Amsoils quality of their products. Amsoil has proven time and time again that it can go the distance, more than a few times my family has driven well beyond the distance advertised, with no concerning lubrication deterioration. The huge cost of regular maintenance is overshadowed by all of the money my family and I have saved by not having to perform highly unnecessary shorter service intervals, the biggest part of the huge expense of owning a vehicle. The money I've saved from being able to extend maintenance intervals with pretty much trouble free service from my vehicles from using Amsoil products is one of the best benefits the Amsoil synthetic
    Bottom Line
    Yes, I would recommend this to a friend.
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  • 5 star rating
    Better than expected
    By  JACOB,  a  Verified Buyer  from  Palm Coast, FL  on  May 26, 2022
    I have a 2003 Ford 6.0 powerstroke. If you know a bit about them, oil has more functions in this motor than usual. Typically, I run T6 Rotella, which is great. Was very surprised when I could feel the difference with this product. Worth the extra money
    Bottom Line
    Yes, I would recommend this to a friend.
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