I've been using the 15-40 Heavy-Duty Diesel and Marine oil in my 2006 GMC 2500 HD Duramax LBZ since I bought it new and now have 287,00 miles on it and many of those miles towing heavy loads in the heat.

I used this in my marine diesel engine. I had some reservations based on past experience with synthetic diesel oil from another manufacturer (noisy operation), but this far exceeded my expectations. Since switching from the industry standard mineral based oil to Amsoil Heavy Duty and Marine Diesel Oil, I have higher oil pressure and cooler operating temps, and the noise level seems lower as well. I am very satisfied.

Folks, I switched to Amsoil at 150,000 miles now I have 400,000 miles on my truck. I believe the quality of Amsoil and there filters are keeping the engine wear down. My last Blackstone oil sample (paraphrasing here) recommended I increase oil change intervals if desired because the sample indicates an engine of around 130,000 miles. I especially enjoy the the super quick delivery to my doorstep.

I changed the oil in my 2010 F 150 to Amsoil and the gas millage has increased by by 4 miles to the gal. I am very happy with the new oil and will keep a eye on the millage to see if it stays good

i use this oil in my 8030 allis-chalmers tractor. this synthetic oil is excellent we get to 20 below zero here in the winter and i use this tractor on the snowblower and the minute the tractor makes one revolution with the starter the oil pressure light is off and it starts way easier with this oil. i am very satisfied with this product. would recommend to anybody who would want to use it. super product.

This is probably the best in the world.

I work my Diesel hard towing doubles in the mountains you can always count on Amsoil to protect your engine

Have used this product since 1997, and still impress with it. Do oil change once a year (approx 25000 kilometers per yr) send an oil sample to Lab and return are excellent. Highly recommended

I have been using this engine oil in my Diesel Pusher Motor coach for 10 years and would not use another oil. I also have the Turbo Drive automatic oil in Allison Transmission and because this transmission is not only very good but it is an expensive one that I only want the best oil in it. I actually replaced the recommended Castrol Transynd oil that was in it to this Amsoil one and noticed that the shifting is smoother and the temperatures are lower during use. I monitor all the engine and transmission activity thru a computer while driving so I actually am seeing what is happening at any time, so, these issues I see and not only feel.

I have been running this oil for 15 years in my 2005 superduty 6.0 diesel. This truck pulls a 16,000 lb fifthwheel many miles a year. Engine does not use any oil, have not had any injector sticking, and no turbo coking. Great customer service and lighting fast shipping.

I have been using amsoil diesel/marine in my 2004 dodge cummins since it was new, never had any issues. the truck has 186000 miles on it and sometimes the oil doese't get changed for 6000 miles but always has plenty of lubricity when changed. Hal

I have a Kubota 8200 farm tractor it has a low oil pressure shut-off in cold weather using conventional motor oil same weight it would crank and shut off using Amsoil diesel marine this stopped so oil is getting through the engine quicker so now I use in all our farm equipment

The absolute best for my 2002 7.3L Diesel Excursion.

Great oil, I use it in my 2006 Century Freightliner, I have over a million miles on it. Wouldn't trust any other oil.

I have a Chevy Silverado 3500 year 2008 410,000 miles on the truck love this product

Over 200,000 miles on F-150 using this oil no issues what so ever with engine.

Have been running in 04 duramax 3/4 ton for 100,000 miles with regular oil change intervals between every 3500 to 5000 miles in a work truck that has towed heavy loads or been under stress for most of its life. Switched to synthetic amsoil at 65,000 miles in engine, plus transmission and all the boxes. Has 179,000 + miles on it now and is still running and working strong. I believe the amsoil and regular oil change intervals has made a difference in the longevity of trucks power train components.