Protect your investment in diesel power and confidently extend drain intervals with our top-grade synthetic diesel oil. AMSOIL Signature Series Max-Duty Synthetic Diesel Oil delivers 6X better wear protection than required by the Detroit Diesel DD13 Scuffing Test for Specification DFS 93K222. Advanced synthetic technology provides excellent viscosity control and outstanding extreme-temperature performance, while minimizing oil consumption. The result: protection that's boosted to the max.
Package sizes include:
Quart Bottles
Gallon Bottles
2.5-Gallon Bottles
30-Gallon Drum
55-Gallon Drum
275-Gallon Tote
Use in diesel engines and, where appropriate, gasoline engines requiring any of the following specifications:
• API CK-4/SN, CJ-4, CI-4+, CF
• Volvo VDS4.5, VDS4, VDS3
• Mack EOS-4.5, EO-O
• Renault RLD-4, RLD-3
• Cummins CES20086, CES20081
• Caterpillar ECF-2, ECF-3, ECF-1-a
• DDC 93K218, 93K215, 93K214
• DFS 93K222
• ACEA E9, E7
• MB 228.31
• MAN 3575
• MTU Type 2.1, II, I
• JASO DH-2
• Allison TES439
• Deutz DQC III-10LA
• Scania LA-2
• Chrysler MS 10902
• Ford WSS-M2C171-F1
Maximum Engine Protection: Wear on rings and cylinder liners leads to increased oil consumption and loss of compression, resulting in reduced horsepower and fuel economy. Independent testing shows AMSOIL Signature Series Max-Duty delivers 6X more wear protection than required by the Detroit Diesel DD13 Scuffing Test for Specification DFS 93K222, delivering the security of providing your diesel the extra protection it deserves.
Using top-tier synthetic base oils, AMSOIL Signature Series Max-Duty is naturally resistant to oxidation and the thickening effects of soot contamination. That, along with boosted detergent/dispersant additives, keeps soot particles suspended independently, helping prevent the formation of larger, wear-causing particles. Viscosity increase is minimized and soot-related wear is controlled. Lower volatility also helps Signature Series Max-Duty retain its viscosity after high-temperature service for maximum engine protection and efficiency.
AMSOIL Signature Series Max-Duty Synthetic Diesel Oil resists thermal (heat) breakdown better than conventional and competing synthetic diesel oils. Unlike conventional oils, Signature Series contains no wax, staying fluid in sub-zero temperatures for easier starting, improved oil flow and reduced wear. Signature Series 0W-40 (DZF) has a broad viscosity range that offers 4X better cold-cranking ability than a 15W-40, making it excellent for use in both hot-operating engines and cold-weather starting extremes.
AMSOIL Signature Series Max-Duty has a low rate of volatility (burn-off), reducing oil consumption during operation and passing less oil vapor into the combustion chamber. It provides up to 76 percent less oil consumption than required by the API CK-4 standard in the Caterpillar-1N oil consumption test.
AMSOIL Signature Series Max-Duty Synthetic Diesel Oil is compatible with other conventional and synthetic engine oils. Mixing AMSOIL diesel oils with other oils, however, will shorten the oil's life expectancy and reduce the performance benefits. AMSOIL does not support extended drain intervals where oils have been mixed.
Aftermarket oil additives are not recommended for use with AMSOIL synthetic diesel oils.
Diesel Engine Service Life
Heavy-Duty On-/Off-Road: Three times (3X) OEM1 recommendation, not to exceed 60,000 miles/600 hours or one year, whichever comes first.
Turbodiesel Pickup: Two times (2X) OEM1 recommendation, not to exceed 25,000 miles or one year, whichever comes first.
Gasoline Engine Service Life
Two times (2X) OEM1 recommendation, not to exceed 15,000 miles or one year, whichever comes first.
Drain intervals may be extended further with oil analysis.
Refer to your owner's manual for OEM drain interval recommendations and guidelines for severe and normal service.
Note: Extended drain intervals are not recommended for performance-modified engines, when using biofuels containing more than 10 percent ethanol or 15 percent biodiesel (B15) or for 2007-2009 Caterpillar* C13 and C15 on-highway engines. Extend drain intervals beyond OEM recommendations in these instances only with oil analysis. Note: 2007-2010 Dodge**, Ford** and GM** turbodiesel pickups are also not recommended for extended drain intervals when using DHD.
This product is not expected to cause health concerns when used for the intended application and according to the recommendations in the Material Safety Data Sheet (MSDS).
Click here to view the MSDS Data Sheet for AMSOIL DEO.
Keep out of the reach of children. Don't pollute. Return used oil to collection centers.
| TYPICAL TECHNICAL PROPERTIES | |
| AMSOIL Signature Series Max-Duty Synthetic Diesel Oil (DEO) | |
| Kinematic Viscosity @ 100°C, cSt (ASTM D-445) | 15.4 |
| Kinematic Viscosity @ 40°C, cSt (ASTM D-445) | 94.5 |
| Viscosity Index (ASTM D-2270) | 173 |
| CCS Viscosity @ -30°C, cP (ASTM D-5293) | 5555 |
| Pour Point °C (°F) (ASTM D-97) | -43 (-45) |
| NOACK Volatility, % weight loss (g/100g) (ASTM D5800) | 9.2 |
| Total Base Number (ASTM D2896) | 10.1 |
| High-Temperature/High-Shear Viscosity, cP (ASTM D5481) | 4.3 |
| Sulfated Ash Content, wt. % | 0.99 |
Product Name: Signature Series Max-Duty Synthetic CK-4 Diesel Oil 5W-40 (DEO)
Current Rating: 4.88out of 5 stars
Votes & Reviews: 60 vote(s) and 61 user reviews.
Reviewed by Pat: 
I use this oil in my 2014 Dodge Ram EcoDiesel. Amsoil updated the oil from 5W-40 to 10W-40 based on Dodge recommendations. Great oil.
Reviewed by Jon Driver:
Under heavy usage and need peace of mind
Reviewed by Chris:
My engine is still running and since I can't see inside it, it must be working.
Reviewed by SG:
Dumped class 3 synthetic rosella t6 for a true synthetic class 4 PAO Amsoil Sig Series 5w-40. Turbo Diesel is running smoother, quieter, cooler and 2-3 mpg boost! Worth the money!
Reviewed by Rick Wysynski:
I was a Royal Purple junkie since it was the only synthetic available to me where I live and got it free. It worked great in my gas truck and other gas vehicles. I switched to Amsoil since I purchased a diesel truck and became a Preferred Customer. Really like that part !!!
The truck runs much better and accelerates better than the Ford oils that were in it and oil change at 25,000 miles is a nice $$ saving feature. I will switch to the new synthetic 5-40 on the next oil change and then extended changes past 25,000 would be nice. I monitor all things done to my truck and log it.
Put 9,000 mikes on the truck in less than 4 months and excellent results !!!
Reviewed by Phil in Tulsa:
I've been using AMSOIL heavy duty diesel oil for years and it has performed extremely well. This year I decided to try the Signature Series Max-Duty and was I amazed. I didn't believe I could tell the difference but the engine runs even smoother. I tow trailers with my truck and protecting the engine is paramount to reduce wear and lengthen the life and this oil delivers.
Reviewed by Kelley:
I use this oil in my skid loaders as well as heavy duty pickups pulling heavy loads daily.
I have been sold for many years after I had 6.0 diesel that dumped all the oil and the only thing that saved the motor was this product.
All the shop had to replace was head gaskets
Reviewed by patrick:
In my Excursion Diesel 250,000 miles
Reviewed by F450:
First, I'll say that I love Amsoil. I run Amsoil in every engine/transmission/differential/etc I own. I'm not sure about this new oil. My oil temp in a Ford 6.7 Powerstroke usually runs about 203 degrees (previous version of Amsoil diesel oil). With this new oil (December it might have come out???) I'm running 7-10 degrees hotter on average. I'll probably try one more oil change with it and if it still runs hotter, I'll have to find another brand.
Reviewed by Dave:
I am astonished at the engine oil life provided by this oil, compared to the Mobil synthetic I used previously. I'm at 14000 km, 80% city, and the computer is telling me I still have 20% oil life. Previously I would get to about 10k and be looking to change. Admittedly I changed to Wix filter at the same time from Oem, so not a 100 % true comparison. Winter, with more idling, will be the real test. Engine seems to be running cooler even in 30C weather- that's hot for us!
Reviewed by Nimble:
Use it a 09 Chevy Duramax, starts great even if it hits 0 or below
Reviewed by John R:
I currently use this product on my 2016 Ram EcoDiesel with no issues and have use the previous 5W40 diesel product on previous diesel pick up trucks and heavy-duty equipment with no complaints. Thank you Amsoil.
Reviewed by Matt:
Engine ,primary and transmission fluid for my fxstdi.
Reviewed by jobu:
i have used Amsoil in the past in a 6.0 powerstroke and didn't really see much difference, tried it again in my 6.7 powerstroke and love it. The motor starts and runs smoother and helped with the mpg
Reviewed by Ryan:
My son uses Amsoil in his 2011 Ford F350. He has many mods on his truck. This is the only oil that he trust.
Reviewed by Rob:
I put this in my Kabota BX25
I was hoping it would quiet the motor and make for easy starting on cold inter days.
It did quite the motor a lot.
Started with no issues.
Reviewed by Big Frank:
New 2017 ford diesel. Outstanding oil. Highly recommend it. Would only use this oil in my new Diesel engine It is so high tech
Reviewed by None:
Ran for 8 thousand miles & love it so far
Reviewed by Dimonic:
I like to do my own oil changes, and avoid all the "additional" services the dealer offers.
Reviewed by Cumminswitit:
My truck and I love this stuff. I run it for a year between changes and love it. Best oil out there
Reviewed by elkoholic:
Truck is used for hauling horses.
Reviewed by Petro:
I use Ams oil in every application of my truck and never have I been let down
Reviewed by MURF:
IN A DODGE SPRINTER
Reviewed by 4B RANCH:
I have three diesel trucks and five diesel tractors, and all are serviced with Amsoil products. Besides extended oil changes, my engines stay clean and trouble free. I would never consider using anything else.
Reviewed by Randy:
I have used this oil for over 18 years in a 7.3 diesel ford-350 4x4 and have had great performance in using it .The engine doesn't have to work as hard with Amsoil synthetic oil 5-40w it runs cooler and less RPMs for the same speed as other oils . If you're not using Amsoil synthetic oils in your engine and truck and or other motor vechicle your missing out on the best performance your motor Vechicles can give you ..
Reviewed by engr:
looks good. I will need more time to fully evaluate it.
Reviewed by truckguy12:
Premium oil for a premium price. Works out in the long run for me with extended drain intervals. I use it in all my diesel business trucks.
Reviewed by Trev:
I use amsoil in all my vehicles, even my lawn mower. This stuff is the bomb, less oil pressure due to better flow, and smother running etc...
Reviewed by J:
Great oil for you engine can't go wrong with full synthetic. Other then manufacture recommendation on oil brand this is the only other brand I use. I'm still old school so 5k oil intervals is cheap insurance for a $67k truck. Oil itself is amazing compared to previous oil used at 5k miles drains Amsoil looks and feels great. Smoother engine idle and smoother engine operation at higher rpm range. I have a digital psi gauge installed and with Amsoil the engine oil psi has maintained same psi throughout the oil intervals the oil temperatures has dropped 8 degrees lower under same driving conditions. I know that's not a professional oil analysis but it's what I've got.
Reviewed by Steve:
I use amsoil in everything I own, from vintage snowmobiles to outboard motors to stihl concrete saws to my cummins to my jeep crd. I swear by your products and have switched a number of people over to it. It's cheap insurance especially when you plan on keeping your investments for a long time. It's the only oil I can count on
Reviewed by DWC521:
My 2016 F350 6.7L runs smoother on this oil
Reviewed by Hurst:
I notice a big difference in mileage and how the truck ran after changing the factory oil to Amsoil. The mileage is up over brand X that I replaced. I've used Amsoil in all my diesel trucks, no complaints!
Reviewed by mistercedric:
I have used this oil for many years in my 3500 GMC. A recent trip of 11000 km with the 25000 mile oil filter did not change the color of the oil it was still as if it came out of the container. Excellent starting in cold weather
Reviewed by Ivan:
Great oil at better than dealership prices.
Why wouldnt you?
Reviewed by 100 MPH:
I love this oil I rely on it with my lively hood. Great stuff.
Reviewed by Danny Boy:
I don't know if my 2013 Ram diesel is protected better by using Amsoil motor oil, but I trust Amsoil research. I believe what Amsoil claims. I can only say this about Amsoil. Only time will tell as the engine ages.
Reviewed by Tamworthsat:
I would buy this top grade again because I once bought the XL grade and notice a slight drop in mileage.
Reviewed by Mark:
I have been using Amzoil in my 2008 Dodge Ram 2500 since the first oil change. I currently have 147,000 miles on it and it doesn't burn a drop of oil, runs smooth and has a ton of power. I believe that using a quality oil with regular oil changes is the key. This stuff is not cheap! Neither is this truck! But to replace it is $68,000. I think the Amzoil is going to give me that quarter million mile mark.
Reviewed by -King D:
Perfect
Reviewed by Benny:
I work my diesel trucks hard. Pull heavy loads 100% of the time. When it's 0° and they start up with quicker oil pressure and less engine clatter, or when it's 95° out and I'm wide open throttle for miles up a long steep grade and my oil temps maintain a steady temperature, I feel more confident my engine will last longer with Amsoil.
Reviewed by 204man:
Cold start 2016 cummins. -23. No problem. Amazing in cold temps.
Reviewed by Frank:
I have been using Amsoil since 1979 and I believe in putting the Best Oil in all my Toys . I use it in my cars,garden tractor , lawn mower , whole house generator , power washer , and my 2 Corvettes ,and in my 2013 Kioti CK35 HST Diesel tractor . I guess you could call me an Amsoil Junkie
Reviewed by Arthur:
I just changed the oil in my 2015 with Amsoil for the first time, because the truck came with 2 years of maintenance when bought new, and if you didn't use it your just wasting money.i am a firm believer in Diesel injector clean, I'm on my second Duramax and have never had a fuel related problem. I'll use Amsoil forever.
Thanks for great products.
Reviewed by Clay:
08 Duramax 250k miles and still going strong. -30 here in winter, starts up with good oil pressure no waiting on the pressure gauge to pick up cold oil.
Reviewed by JERRY:
When Amsoil produced a oil meeting Chrysler's requirements (2015 Jeep GC 3.0 Diesel) I jumped on it as I have always had good experience with Amsoil oil.
Reviewed by Marc:
Only product I use. The BEST!
I use it with AMSOIL FF and bypass filters.
Reviewed by Rob:
Excellent product, my 2005 Cummins runs smoother than it ever has. I feel very confident pulling some of the heavy loads that I do, knowing that this oil will stand up to whatever I can put it through.
Reviewed by Mark:
Very pleased with the purchase. Regens intervals have increased by a significant margin, particularly in the city driving.
Reviewed by Jeff:
I've been using this in my 2004 Dodge Cummins diesel for 12 years and 120,000 miles and it still runs like it was new.
Reviewed by Douglas:
Best oil on the market ! My 2011 Ford F 250 6.7 deisel has 99.687 miles on it and uses no oil between changes !!!
Reviewed by Dk:
Truck not plugged in -40c slow crank still started. I believe 5-40 made the difference. Good oil
Reviewed by Novy:
Been using this oil for a while and like it. Cold weather starts a breeze!!!!!!
Reviewed by big boy:
could not think of a better oil. longevity, performance, and mileage difference is evident. recommend it for all diesel vehicles. No complaints.
Reviewed by Ihmachine:
I use amsoil in my 07 diesel truck, I have 7,000 miles on the oil change and still clean according to the lab test! I've used amsoil in different motors and I'm a believer, this oil is spectacular from my personal experience.
Reviewed by BWW:
Have been using this product in my 2011 ford diesel since day one. I put on about 14,000 miles a year and change my oil once a year. I have never had to add oil between oil changes. I'm amazed even at change time the oil is still so clear its hard to read the dip stick. Ive been trying to figure out something to put on the dip stick to see the oil easier.
Reviewed by Kevin:
I have been using AMSOIL Premium 5W-40 Synthetic Diesel Oil for the last five years and I have never had any issues starting when the temperature drops below -30C/-22F.
I switched to AMSOIL after my first winter because I was not happy with the cold weather starting performance of other full-synthetic diesel oils.
Reviewed by Master Bear:
Amsoil Premium 5W-40 Synthetic Diesel Oil is the best! I have used it on my diesel vehicles for years, and have been quite satisfied with its longevity and performance.
Reviewed by JP:
2011 F250 6.7L. Great oil with great customer service to back it.
Reviewed by Mike:
Excellent performance in my 6.7 power stroke
Reviewed by Ronald Glen:
Switched over my 6.0 Powerstroke to Amsoil DEO. After some contemplation, I decided to go with Amsoil for few dollars more than Rotella. I am glad with the decision as the engine has become noticeably smoother. This indicates lower internal friction which will translate into longer engine life. I am already getting 50-70 miles more miles per tank of diesel, which justifies for the slight premium in the price.
Also it appears that I can go longer on the oil. I personally don't believe & was not planning on extended drain intervals as suggested by Amsoil. But with the way things are going, I feel comfortable going 50% more on the oil, which again justifies the higher cost of the oil.
I'll continue with Amsoil DEO, its working out to be lot less expensive than RT6.
Re: Much smoother than RT6
To overcome extended drain anxiety, consider doing used oil analysis 1000 miles before scheduled oil change.
You can confidently, continue with the oil if the report indicates all the levels to be within spec. Repeat the oil analysis again until the report recommends changing the oil.
This is the most informed and scientific way to establish oil drain intervals. We see conventional oils breaking down below spec before their scheduled interval, indicating accelerated engine wear (even with frequent and regular oil changes). Therefore, the condition of the oil should be the factor that call for an oil change. Replied by Tech Admin
I only run this oil in my diesels
I have four dodge diesels and a cat powered welding machine and I run this oil year round with zero issues. I do oil changes every 25000kms.