Product Reviewed: Synthetic Heavy-Duty Diesel & Marine Motor Oil SAE 15W-40 (AME)
Current Rating: 4.91 out of 5 stars
Votes & Reviews: 316 vote(s) and 236 user reviews.
Reviewed by Diesel DDT: 
We have been using this oil in our diesels for over 8 years and it has never let me down. We had a fleet of 150 gensets and 50 semis. Not once did we have an engine failure due to lubrication qualities with this oil. Our engines in the gensets lasted 26,000 hrs before we would pull them out of service to rebuild. I have used this oil in my personal diesel pickups and have never been disappointed. I will run this oil for life.
Reviewed by Repoman:
This is used in my 95 F250 7.3 diesel & i credit it with keeping it running well for over 400k miles
Reviewed by John H:
We have a diesel Pusher motorhome and since using this product I figure my engine (Cummins) runs smoother and cooler, along with the extended mileage, it is a no brainer for performance and cost savings overmore frequent oil changes. I installing a By Pass filter to clean the oil even more than the stock filter does, My coach has a Allison Transmission so that gets the 'TORQUE DRIVE " Synthetic oil and the rear end has the 80/140 oil too. Nothing but the best for us for sure.
Reviewed by 4 to 1:
Chev duramax des
Reviewed by Eric:
Use it on both of my 7.3s love it
Reviewed by Moomoo:
Great product about some it up used it four years. Not only use 14-40 in my 2003 dodge i use amsoil in all my stuff
Reviewed by Smoke:
Are used this product on four different trucks since 2007 to my current 2016 Duramax diesel I would not use any other oil
Reviewed by Hhdreamer:
I am so thankful that Amsoil still makes this oil. I use it in my diesel farm equipment and truck that I don't want to use the disasterous CJ class of oils!!!
Thank you Amsoil!
Reviewed by Horseman:
Been using in my 1999 F250 diesel since I bought it in 2005 with 57K miles. Engine now has 227,000 miles and still runs smooth and burns very little oil . I learned when I bought my truck that the fuel injectors are lubricated with the engine oil and I wanted the very best oil in my engine. I have had to replace only one fuel injector to this date.
Reviewed by E man:
Get a lot more mile from this oil.
Reviewed by Jerry:
Tractor
Reviewed by rob:
this motor oil ,i got no comment to say ,the fluid is great, the antiwear formulars that is blended in is good and it do not burn within oil change inteval,i normally replace every 20,000 to 25000 miles on the ram with the 6.7 diesel.
Reviewed by Perfered Customer 99:
Been using this oil since I have had 25,000 miles on my 05 duramax now have 128,000 plus miles and it still going strong. Now I don't put as many miles on the truck and I only have to change the oil once a year. Also use AMSOIL filters.
Reviewed by Morgan:
I change my oil every 10-20k in my 99 cummins. Its still gold in colour after 5k.i proudly show everyone
Reviewed by pf250:
I pull a 38 ft 5th wheel. The oil gives me the extra miles I wanted between oil changes. I have Gained over a mile per gallon in millage after switching to AMSOIL
Reviewed by TJ:
change oil once per year after about 50 hours of operation
Reviewed by luke:
Use in my work truck that is constantly pulling equipment .
Reviewed by luke:
Use in my work truck that is constantly pulling equipment .
Reviewed by Greg:
I run this in my 03 Cummins 5.9. Great oil, have 356,000 on her.
Reviewed by Rod:
Duramax diesel
Reviewed by Duramax:
Put in an 07 duramax fully deleted great
Put In a 13 duramax fully deleted typewriter ticks slightly
Put in a 2015 duramax fully deleted typewriter ticks really bad
Reviewed by Chief:
Recommended by a friend, I have purchased this product since I bought my 2004 Dodge Heavy Duty. Still runs great. I run Donaldson oil filter.
Reviewed by Stan the man:
I use Amsoil products in all my vehicles
Reviewed by Doc:
I use this particular product in both my diesel powered Motor home, and my F350 truck. I used oil testing to determine oil change periods and have saved considerable money over fossil based oils. In addition easier starts, and increased mileage have added to the positive results of the AMSOIL use
Reviewed by Keith:
Been using in 06 chevy 3500 has 253,000 uses a qt, in 25000 miles can't complain !
Reviewed by Dave:
Been using this for years and have been validated time and time again. This is the best!
Reviewed by Big John:
Run it in both of my duramax trucks one has 260 thousand miles other one Amsoil is all it's ever had both all clean as gold
Reviewed by MIXER FIXER:
ALL MY CARS AND RV USE AMSOIL OIL AND FILTERS AND HAVE NOT HAD ANY ISSUES USING THEM. ALL RUN COOLER AND SMOOTHER. THE ONLY OIL I WIL USE. ALSO USE ALL THERE OTHER PRODUCTS TOO.
Reviewed by Jim:
I tried this oil the first time I ran it for 14,000 miles it test still good. The second time I ran it 19,000 miles, it still tested good. I may change the filter at 20,000 and go for 25,000 this time we will see how it goes. I think my Duramax likes it too!!!
Reviewed by Jim the driver:
I tried this oil the first time I ran it for 14,000 miles it test still good. The second time I ran it 19,000 miles, it still tested good. I may change the filter at 20,000 and go for 25,000 this time we will see how it goes. I think my Duramax likes it too!!!
Reviewed by B-:
Excellent oil!! Performs just like all Amsoil products do.
Reviewed by Silver Bullet:
Run this oil in my 8000# open diesel truck. it has been ran in this truck from the time it was new.
Reviewed by Verno:
Use Amsoil 15W40 in my 82 VW Westfalia and would have anything else. Just returned from a coast to coast trip (12500 miles in total, mountains, snow, heat and lots of cold starts and the old van never let us down. Credit to Amsoil!
Reviewed by JRT:
I run the 15w-40 diesel/marine oil in my 99 Peterbilt. I've had excellent like with it for 3 years now and the extended drain intervals save me a lot of money per year.
Reviewed by ZH:
I have been running this oil for seven years. I ran it in a fleet of 125 Generators, 25 Loaders, and 40 Kenworth semis. I never once in 3 years had an engine failure. These pieces of equipment ran around the clock in the oil fields. Our generators would run 26,000 Hours before we would bring them in for a rebuild. We would take them out of service for a rebuild, the engines never failed. I would reccomend this product to anyone and I would put it against any other oil on the market. I run it in all my personal vehicles and engines. I will be an amsoil customer for life.
Reviewed by Runky:
I've used this oil in my diesel pick up since I bought it in 2005. It's had 11 oil changes in 11 years and 142000 miles and runs great. All the fluids in my vehicles are Amsoil products. Stick with the best.
Reviewed by Brad:
2002 duramax lb7, works great
Reviewed by Robert:
Great product. Run nothing but Amzoil in all vehicles including off road vehicles and boat
Reviewed by Toon:
Have used this for years in my trucks .
Reviewed by Art:
Love this oil. Why don't you guys send stickers anymore?
Reviewed by Sfa:
This is the best oil that I've found for my duramax
Reviewed by Frank:
I have used this product in my 05 chev duramax for years. My truck has 155000 miles and I'm sure the oil has a lot to do with it
Reviewed by Mini me:
I use this oil In my dmax
Reviewed by Cruiser:
Bought the 2012 Ram 3500 18 months ago. Didn't know what oil the previous owner used but took the truck home. Changed oil to amsoil 15-40 at 22000 miles. I currently have 90000 on the truck and performs great. I also pull a 39 ft 5th wheel
Reviewed by Charlie:
Love the extended drain cycles. I ran my truck for 10,000 miles before I drained it. Next time I will do an oil analysis to see if I can go longer
Reviewed by Big Gold:
The reason I went with Amsoil was because I tow heavy up the mountains and wanted a full synthetic that I knew I could depend on. This full synthetic 15w-40 does everything I need it to. Keeps my engine running like new and I only have to change it every 10,000 miles. Awesome job, you definitely have a lifetime customer!
Reviewed by Chris:
Amsoil is the best synthetic motor oil I have used period. I use this in all my trucks and equipment and with very high miles and high hours. Each and everyone operates excellent.
Reviewed by Joey:
I have been using Amsoil Diesel marine oil for over 10 years on my 2004 Dodge common rail I have no complaints for the price I pay for....(You get what you pay for) Good product no leaks,overheating,knocking or any issues with oil. 123,000 miles and going strong.....Even my diffs and trans use Amsoil...
Reviewed by Mark:
This is a fantastic oil. I love the fact my oil change intervals are longer. I have been using this for many years. Almost have 200,000 miles on my 7.3 liter and its still going strong.
Reviewed by Casey:
Drive a lot this product seems to help truck run smoother
Reviewed by Decent:
AMSOIL is truly the best real Synthetic oil out there and i will not
use any other oil for my trucks and cars. Thank You AMSOIL for standing by your product and so do I !
Kevin Broyles
Reviewed by Capt. Cocomojo:
Run my offshore boats Hard, keep them at running for hours at 5500 rpm.
My custom built diesel truck tows all over the country carrying heavy loads.
Run the Marine amsoil in both.
Blew a coolant hose pulling my offshore boat from Bodega bay , ran for 27 miles with no coolant till I got home. Diesel never once thought about overheating.
Reviewed by Mark:
Used for years in truck.
Reviewed by Mellow Yellow:
I have a 1982 Diesel Westfalia with a 1.9TD engine. I am
almost scared to try another brand and definitely never another grade of Oil. I did that because at the time I was on vacation and I couldn't find the Amsoil product. Within one tankful of diesel I lost my turbo. Also, I also cannot find any other reason for my decreased mileage when I did switch brands. I admit I am a bit anal about my old Westy but with careful, consistent driving I can resolve all the variables. Despite the difficulty in finding a local supplier and the increased expense verses using a local sourced brand I will always choose Amsoil brand. Having gone through 3 engines from other causes, it's just not worth the risk to switch.
Thank you Amsoil.
Reviewed by Don't have one:
I have been using these products for many years in gasoline and diesel applications. Big plus is the ability to set and forget for a year is quite nice. With having multiple vehicles in my driveway and having to work on many others means my maintenance needs to be transparent to all of the other work. This product in particular has kept my engine safe and worry free. My truck is from the showroom floor in 2003 (6.0l) and she is not allowed into the shop accept for programming or tires. Those are my rules as well as for all the rest in my driveway. I will not accept inferior products. Thank you Amsoil.
Reviewed by TJ:
My 1996 Ford F-250, 7.3 Powerstroke never leaked oil until I started using this product. Only 137000 miles.
Works well in inboard boat engine.
Reviewed by Montague Wrangler:
In my diesel truck I have tested my oil using the AMSOIL filter after 15000 miles and it always tested good and ready dfor additional mileage.
Reviewed by Montague Wrangler:
In my diesel truck I have tested my oil using the AMSOIL filter after 15000 miles and it always tested good and ready dfor additional mileage.
Reviewed by Big A:
I have been using this in my 5.9 Cummins for four years now. I gained 2 mpg since changing all of the fluids over to Amsoil.
Reviewed by Andy:
I really like this oil. I was using Rotella and burning a gallon every 2 weeks. Since I switched I don't add any oil throughout the 500 hour service. I also get better fuel mileage. I was averaging around 4.8-5 now I average 5.5-5.8
Reviewed by Boog:
I have used amsoil for years . It's the best & has always improved on its products.
Reviewed by muxdragon:
Lasts a full year before the next oil change. I like the 2.5 Gallon jugs the best. Great product!
Reviewed by ANITA:
We use in 95 Freightliner. We have been using for 4 years or more.
Reviewed by Ric:
After 500 miles, the oil is still honey colored, not black like the other oils I have used. This oil is great.
Reviewed by Mike:
Been using this for 10 years now and never had any trouble. Great protection and better in cold winter starts
Reviewed by Rabbit:
I have used this oil from my first oil change at 5,000 miles with Amsoil absolute filters. Test oil at 25000miles change filter and run another 10000 miles. Tests have all came back with no viscosity breakdown, no metals or any other abnormalities. I now have 160,000 miles and have never had to add any oil other than what it takes to fill the filter. The service is second to none and so are Amsoil products.
Reviewed by Bob:
Love Amsoil and it's reliability
Reviewed by Jose:
I BEAM USE THIS PRODUCT FOR MY DIESEL TRUCK NICE PRODUCT
Reviewed by Gennaro:
I use this product in my 28 carolina classic with 2 4bcummins diesel engines. the oil has kept the engines clean and running smooth, with no smoke. the engines have 1300 hours on them.
Reviewed by Keith:
Exceeds expectations. Ordinarily, when I used other motor oils discoloration takes place within 1 to 2000 miles. Thus far since I switched to Amsoil, 3000 miles, no discoloration and no oil consumption.
Reviewed by Kyle:
This is the best and only oil for my powerstroke.
Reviewed by Stephan:
A great heavy duty diesel oil with high 12 total base number. Works great , quiet's engine noise, keeps good oil pressure and engine clean.
Reviewed by Stephan:
Runs great in my old diesel and my new one!
Reviewed by Andriy:
555
Reviewed by John:
Performs as expected but on the pricey side.
Reviewed by Ted:
use it in my dodge truck, very pleased
Reviewed by Robert:
Use it in my Duremax 350,000 on it does not use a drop of oil between changes.
Reviewed by Jagath:
I use it on my Ram 2500 with 5.9 Cummins engine and it's humming and I use the 1 micron bypass filter
Reviewed by Darren:
I have used this oil in my 2006 Duramax since it's had 10,000 miles on it.
I currently have 123,000 miles on it and no problems..
Reviewed by Greg:
I have been using this product in my diesel pick up for years now. 360,000 miles and going strong.
Reviewed by Doug:
Could tell the difference the first time I changed to this oil. The truck runs smoother and uses very little between changes.
Reviewed by John:
Love this oil for my '05 Duramax.
Reviewed by Jimmie:
Used AMSOIL in '97 F250 - ran great for the 15 years I had it hauling horses to shows across the country for 250k miles. Replaced this truck with '06 F350 in 2013 - not hauling as much or as far but still trusting AMSOIL.
Reviewed by WILLIAM:
Best oil for my Dodge Ram 2500 5.9 Diesel.
Reviewed by David:
I have used this oil since the very first oil change on my 04 Chevy Duramax. At 205K they pulled the valve covers to change out the injectors and it still looked factory new. No discoloration of the rocker arms or any build up. Just like new. Best thing I've ever done for my vehicles.
Reviewed by Anthony:
first time user for older cummins 5.9 hope it holds up to claims only thing i would ask for when purchasing amzoil is giving a sticker for window to right next oil change on
Reviewed by Daniel:
I used this oil in my Sea Ray Sundancer whit 350 Mercruiser for 4 years and the Gear lube swell
Reviewed by Joe:
Have 395,000 miles on a 1999 Ford F-250 7.3 diesel did compression test at 380,000 was 3 cylinders at 410 rest at 420 change my oil every 10,000 it can only be the oil that caused such longevity.
Reviewed by
Dietter:
Use this on my F250 6.0 last couple of years (220000miles)
Reviewed by Eric:
Great oil.
Reviewed by Britman:
Great product to keep your engine running at it's peak performance. Used it in my 2006 Dodge Ram 2500 for 152,000 miles. Plan to use in my new Ram 2500.
Reviewed by Smitty:
My vehicle has 245,000 miles using
this product plus others and I am pleased with all of them.
However, my rating of four stars is because you need to continue to produce quality products, stick to your excellent lab testing, research, upgrades and improvements, while keeping affordable prices. When you think you have accomplished all this I will change my rating to five stars.
Reviewed by Rick:
By switching to Amsoil i have seen better gas mileage and i don't have to worry about changing my oil while on the road snowbirding . I just change once a year now and still get better lubrication on my new Ram .
Reviewed by KT:
Love Amsoil! Use it on my vehicle and all my equipment. #1
Reviewed by Bullitt 47:
I have used Amsoil products in my truck since it had 20,000 miles on it. I used the 15-49 heavy duty and marine oil in the engine and Amsoil transmission fluid. The differential oil was drained and Amsoil gear oil was used.
The truck just turned 150,000 miles. I can honestly say that I have not experienced any problems with any of these components. The truck was used for most of it's miles for towing a 5th wheel camper around the country, until 3 years ago. The transmission ran cool and very efficiently. The differential, runs quietly and smoothly. The engine, runs like new. I have had to replace the glow plugs, which is normal maintenance, otherwise, the engine runs like new and maintains the power that it had when new.
I recently replaced the engine oil in our diesel motor home, and expect the same results.
Extended oil changes, makes it possible to travel longer distances without the inconvenience of stopping for oil changes. That saves a lot of
time and ends in less expense. I'll soon be replacing the transmission fluid to Amsoil fluid as well.
Great products, with more confidence, less worry about break downs and less expense. Couldn't ask for more.
Reviewed by Joe:
I use this oil in my truck
Reviewed by Greg:
I own a 2002 Ford F-250 with a 7.3 diesel with 354,000 miles on it. I have been using Amsoil diesel and marine oil for over 200,000 miles engine is running fine with very little oil consumption. Ialso have Amsoil
products in the transmission and differentials. I also use Amsoil products in my 4-stroke outboard motor. I'm
sold on Amsoil.
Reviewed by Tc:
Truck is much quieter with full synthetic. Also starts much easier in cold weather. Using amsoil in truck for 2 years and have since been using in all my vehicles with no complaints
Reviewed by ray:
Years ago, I had bought a used commercial wood chipper from a gentleman in Pennsylvania. He was formerly a Navy mechanic now retired. He told me he always used Amsoil and recommended it highly to be used in the chipper. Fast forward 6 years and we are still using Amsoil in all our machinery, trucks, backhoes, tractors, lifts etc. Need I say more?
Loyal Customer from New York state
Ray H
Canada
United States
I use this product religiously!
I like the fact that I change it only once a year!