Product Reviewed: Signature Series Max-Duty Synthetic CK-4 Diesel Oil 15W-40 (DME)
Current Rating: 4.92 out of 5 stars
Votes & Reviews: 284 vote(s) and 373 user reviews.
Reviewed by Teddybear: 
You can't go wrong with the best of oil produced on the planet
Peace of mind means everything and Amsoil gives you that peace of mind
Reviewed by Ron:
Use this in my 2015 super duty 1 ton dully.
A do a lot of heavy towing long distances
Reviewed by Gmc 2500 Diesel die hard.:
I use the product due to the turbo in the Diesel engine. I want to run the best that can withstand the heat produce by the turbo
Reviewed by CLYDESDALE:
I have a 2011 Chevy one ton dually long bed . Now over 100,000 miles and is running great I feel because I have used Amsoil since day one . I have used every brand with prior vehicles and always go back to Amsoil.
Reviewed by Bobcat1:
Buy diesel, gas oil plus PI for my gas vehicles. Amsoils is the best!
Reviewed by RRDan:
Been using Amsoil HD Diesel oil for many years in Ford Turbo SDuty. Best oil out there!
Reviewed by Whale pilot:
I'm running the 15w-40 Amsoil Signature Diesel in my Corvair air cooled engine in my 22 foot RV. Very heavy duty use for a 3 liter engine from the '60's, and it performs perfectly, along with the Amsoil 75w90 Severe Gear in my differential, and Amsoil ATF in my Powerglide transmission. I use nothing but Amsoil products in my 17 Prius, the 16 Subaru Forester Turbo, And every car I have owned in the last 15 years, and will continue to do so.
Reviewed by Danny Boy:
I like to take extra care of cars that I love. For those cars, I only use Amsoil products. Why? I trust and appreciate the information and research they provide. I'll pay extra for that trust.
Reviewed by Dark Cloud:
Best oil out there. Installed a bypass filter system as well. Very happy with all aspects. Installation was simple
Reviewed by El viejito:
I got two diesels trucks and I bean use this products for few years I like how keep my trucks running great
Reviewed by Moongypsy:
Yearly oil changes, how good is that!
Reviewed by Adam:
Used for oil change in 2005 Chevy Duramax diesel, have been using AMSOIL for years now, great for extended oil change intervals have no complaints about product thus far.
Reviewed by Dave:
I have been using Amsoil for many years. Amsoil is the only product I put in my machines! If you don't have time or inclination to change your own oil, buy and take it to whoever does your oil changes you will still safe money and your vehicle will love you.
Reviewed by Bill:
I run this oil and only this oil. Do changes every 20,000 miles and never have to add any oil during this time.
Reviewed by Mark:
I'm using this in my Onan air cooled generator in my motorhome.
Has run all day in some fairly hot temperatures (mid 90s) with no oil breakdown and generator uses Very little oil between scheduled changes.
Reviewed by Tanker Man:
I'm using this in my diesel pick up. I can't believe how much smoother it runs. And the mileage improved so much I thought the trip computer was broken.
Reviewed by BG:
Amsoil is a great oil. I personally change oil in 8 automobiles and light trucks. Also 1 motorcycle and two lawnmowers. My highest mileage is 200250 miles. I can tell you that Amsoil and their filters will do a superior job. The only down side is the shipping charges. Amsoil is priced about the same as Mobile 1, but the charges mean you pay top dollar.
Reviewed by Rob:
I use this product for two reasons. It offers me excellent protection and performance in
my Diesel engines and because the durability is so good I have flexibility on my service
schedule. My schedule may change and the weather here in New England doesn't always cooperate
and these products let me service at my convenience.
Reviewed by Toad:
so far so good . I believe in Amsoil . I expect the best from this oil . My vehicles depends on it ! I run this in everything I own!!!
Reviewed by Michael:
I use it in conjunction with the Amsoil bypass filter.
Usually Change oil after 20,000 miles or so.
It's great oil, as is your trans and differential oil.
Reviewed by Hey_U:
I use every product I need for our truck and RV and yard equipment.
Reviewed by gofastman:
I have used amsoil in everything i got for the past 10 years, and i cant say enough about it.
Reviewed by obars:
KIt was a nerve racking decision to change to Amsoil in my Old 1993 Dodge Cummins. I really hope it holds up. So far So Good.
Reviewed by Issac:
I purchased this for a buddy he has had no complaints. The shipping speed is awesome.
Reviewed by Elkjr:
Used for my F450
Reviewed by Jeff_Moore3:
Just what the dr. ordered. cooler running longer running less oils changes. fantastic product
Reviewed by Farmer Jeff:
Use in my 2003 Ford 6 liter powerstroke engine and tractor
No problems with the engines and provides great value
Reviewed by Jason:
I have changed all fluids to AMSOIL. The oil viscosity is superior to any on the market. I do the recommended oil change to may 2500HD Duramax. Even after a 10,000 mile oil change the lubrication in the oil is still as if it were brand new. AMSOIL is the best to run in any motor. Give it a shot you have nothing to loose with using AMSOIL products.
Reviewed by BladerunnerRet.:
I live in a cold climate and have never had to use engine block heaters in winter.
Reviewed by Mikey:
Increase oil pressure and smoother idle.
Reviewed by Velcro_Ninja:
I really appreciate the ability to use the "My Garage" to identify the products and capacities listed for each of my vehicles. That with Amsoil's excellent write ups on their products
gives me a piece of mind that I have the right fluids for each vehicle.
This oil has all the additives my old truck's diesel needs to stay running for another 250,000 miles.
Reviewed by
Ford F-150:
great oil. last a long time with the proper bypass set up.
Reviewed by Dodgeram:
great oil. last a long time with the proper bypass set up.
Reviewed by old shop teacher:
Excellent fluid, haven't used anything else for years, thanks
Reviewed by 9quad:
Amsoil is an ansome products.
Reviewed by Kevin:
2007 Dodge 6.7, engine never sounded smoother. Best investment I've made.
Reviewed by California
Buckeye:
Everything I own I use Amsoil in. 2 stroke, 4 stroke, car, truck, trailer, motorcycles... Everything!
Reviewed by Dabear:
Diesel
Reviewed by Big T:
I run this in my 07 duramax it extended my oil change interval from every 5000 miles to every 12000 miles and my truck runs cooler plus I picked up over a mile per gallon on fuel mileage
Reviewed by Nica:
I noticed I get a better fuel gas mileage
Reviewed by L.:
I have been running this oil for over 12 years on my F350 7.3L Diesel. Still running strong.
Reviewed by Mitchell:
Always quality. I run this in my 2009 Ram 6.7 Cummins. Been running nothing but Amsoil since I bought it in 2010 and no issues.
I also use Amsoil Signature 5w30 in my hotrods too. I have a 1967 Chevelle SS with Chevrolet crate 502 as well as a 2013 Camaro SS 1LE
I never worry about oil related issues with Amsoil.
Reviewed by Tom:
I have used this product in my 05 Dodge 2500 for over 5 years and hasn't let me down. Great protection and good in the could mouths with could starting
Reviewed by Robert:
Bought a new GMC Denali and I will use NO other oil it a $60K plus vehicle!
Reviewed by Eldon:
This is the only oil I have used in my 2008 Chevy 3500 HD truck since the first oil change. At this time it is not a high mileage truck and generally change the oil due to time limitation and not mileage. However when the truck is being used it is under somewhat severe conditions and I trust Amsoil to take care of it. I will not at this time consider any other engine lubricant for this truck.
Reviewed by Dk:
Truck not plugged in -40c slow crank still started. I believe 5-40 made the difference. Good oil.
2005 dodge 2500 5.9 cummins
I would recommend this to a friend.
Reviewed by Uncle Denny:
I've been using AMS 15w-40 and the 25000mile filter for over 170,000 miles and have been completely satisfied.The fact that I don't have to take the time to get an oil change every 3000 to 5000 miles helps a guy like me who's on call 24/7.
Reviewed by J:
Using the premium synthetic oil in a 03 cummins, instantly noticed the truck idling better. Glad to extend time between oil changes as well.
Reviewed by RMS:
I think the products are great. Been using them for a long time.
Reviewed by Larry:
I began using AMSOIL 15w-40
Synthetic Diesel oil 3 years ago. I can tell a definite difference in the performance of the truck & there has been increased fuel mileage with & without towing my 5th-wheel. I also have extended the interval of oil changes to 15,000 to 18,000 miles.
Based on my positive results with this product I also had my transmission fluid changed to Amsoil.
Reviewed by Sam:
I Can always count on great quality and fast shipments from Amsoil. I have only used there product on my 2007 GMC Diesel truck from the day I purchased it brand new.
Reviewed by RVer Al:
This product ROCKS! Have used it in my diesel truck since my first oil change in 2006. My truck has 170,000 miles and still runs like a top and still pulls my 5th wheel all over the USA. Also use an Amsoil oil filter and together they are the best in my humble opinion.
Reviewed by Fred climbs Colorado 14 teeners:
I use The 15-40W in my 2014 Ram 3500 with a Cummins 6.7 diesel engine. I pull a cargo trailer daily for my construction business and also have a 40 foot 5th wheel trailer that I am on the road with 45 - 60 days a year. I never have to worry if the engine is being well lubricated.
Reviewed by Mat:
I have been using amsoil in my truck form the day I got it about 5 years ago, Chevy silverado 2500hd Duramax and I have to change my injectors out at 169000 miles the inside of my engine was so clean you could have ate off it. I now have 240000 miles on the truck and drive it as a daily driver over a 100 miles a day. And still use amsoil
Reviewed by Bob L:
Our duramax is a daily driver along with pulling a 43 ft toy hauler. I will be purchasing other products also.
Reviewed by ASAPIE:
I have used this product for many years and I have had great results. I am glade I came across amsoil the product has saved me alot of money.
Reviewed by Tony:
Duramax 6.6 runs quiet excellent feul mileage
Reviewed by Bruce:
Have used AMS Oil for years and it has performed as advertised. Was always a little tough to find a salesperson close to home now it is very simple to order and delivery was fast.
Reviewed by killer tom:
Did an oil change and filter and first week I notice that the engine had smoothed out , and my mileage went from 11.3 liters per 100 k down to 10.6, that's just in 22 kilometer ride to work .Can't wait for a highway run coming in September.
Reviewed by ca2500:
Can't say I had any issue in my 2014 Duramax but for the cost I will be buying something else. I just cant stand lettingmy truck go 10k++ miles on a single oil change but that's just me.
Reviewed by onetexasoldman:
have always used Amsoil
had my order within a couple days very fast
Reviewed by Jeff:
I operate a 2013 Ram 3500 I use Amsoil oil along with Amsoil bypass filtration for a 45000 mile oil change intervals with clean oil analysis
Reviewed by Pete:
Been using the oil since the vehicle had reached 25000 miles. Now it has just short of 120,000 miles. The oil lasts one year. I notice no oil comsumsion between oil changes. Use the truck to pull trailers beside just normal driving. Also belive that the oil aids in cold starts during the winter months. Starting in sub zero weather has not been an issue as todate.
Reviewed by Mac:
I switched from the standard Rotella 15W-40 about 1.5 years ago to the Amsoil 15W-40, and was the best thing I could have
done! Though some of the new diesels are rated for 7500 mile oil changes, when using Rotella I still changed it every 3k miles. With the new emissions on these trucks, the regular oil doesn't last near as long. After only 3k miles, the oil was almost as thin as water, and the lubricity was nearly gone.
After switching to Amsoil, I can go the full 7500 miles and then some (with oil analysis), and the oil still feels like new. I have since started using Amsoil to replace all the fluids in my truck.
Reviewed by Underwaydayz:
Amazing. I have noticeable temperature drops. I run it past the recommended oil change intervals, although that is not recommended. Combined with the Wix filter and it starts easy, runs cooler, and longer intervals. Not a single bad thing to say.
Reviewed by Oscar the Fishaholic:
My brother has owned an F250 Diesel for over 10 years. He told me that his truck performs the same as it did 10 years ago and he has had no fuel injector or motor problems. His friends have had those kinds of problems with their trucks. The difference he said is that he has been using AMSoil in this engine and transmission, and his friends did not. So when I bought my GMC 2500HD Diesel, I bought AMSoil for my truck. Their record is impressive. If I can trust my brother, who can I trust?
Reviewed by Pete:
I have used this oil in my own Cummins engines since 1996.
Reviewed by Happy Camper:
I have been using Amsoil in my diesel towing vehicles sense 2004, when I purchased my first diesel GMC 2500 pickup. I tow a 10,000 pound Airstream
Travel Trailer 10,000 to 15,000 miles a year, and change my oil one time each year. I have used an Amsoil Duai Filter System with the Bypass filter. I change the Full Flow Filter two times per year, and the Bypass filter one time. I got my oil analyzed each year just before my oil change for six years. I never had the lab recommend I change the oil. I put 125,000 miles om my first Amsoil truck, then sold it to a friend in 2014. The oil I am reviewing was bought for that friend, that is stil towing a Travel Trailer and changing the oil like I did.
I now have a 2015 Chevy 3500 Diesel set up just like my 2004 GMC was for Amsoil and dual filters. The order for this oil also included the oil and filters for my new truck. I look forward to getting the same results with this truck doing the same job.
Reviewed by R.V. Transporter:
I use Amsoil in my 2015 F-250. This oil holds up under the stresses that come with running 11 hrs. a day 5 days a week in commercial use. My 2015 already has 155k miles on it thanks to Amsoil, without any engine problems. I have tried other oils, even Royal Purple Duralec, but none compare to the 15-40's strengths when under the high temperatures of Summer in the south and the cold temperatures of the north in Winter.
Reviewed by Bryan:
I have been using Amsoil for many years I use nothing but Amsoil in my vehicles I have a Duramax diesel 6.6 2011 In my opinion Amsoil is the best synthetic oil on the market .
Reviewed by Smart business owner:
Have used amsoil but stopped because the distributor was trying to get me to invest into get rich quick schemes
Reviewed by Bill Ward:
I am using the 15W-40 Premium Synthetic from AMSOIL right from new, enjoying extended drains and great fuel mileage. The truck is 9 months old and has 87,000 km already, also switched the transmission and diffs over to AMSOIL.
Canada
United States
this product is the only one I use
We have three dodge diesels and two gas vehicles and its the only product I use, Some fuel filters they don't have and I use Wix for that. they don't make a fuel filter for my Cummins motors or I would use them for them.