Customer Ratings & Reviews

The 15w-40 heavy duty diesel and marine oil is the only oil I’d use in my old Dodge Cummins 24 valve with a flat tappet valve train. The newer CK-4 rates diesel engine oils are designed for the newer emissions engines with a DPF and roller valve trains. The CK-4 oils don’t have the additive package needed to protect the older diesels because those very lubrication & detergent additives, zinc, phosphorus, & calcium, will damage the DPF and emissions equipment on newer diesels. Oil manufacturers will say the newer CK-4 and higher oils are backwards compatible, but they truly aren’t. This is coming from a guy that has an AA degree in diesel mechanics, 37 years working for a heavy equipment dealership, 17 years as a HD mechanic, 3 years as a T/C which also involved managing the oil lab, and the last 17 as a product support rep. I truly hope Amsoil continues to keep the HD 15w-40 diesel & marine oil in their line up.

My last conversation with one of your reps. Im so pleased to hear that your corporation has a location now in Dubai and Iran. Hopefully not Israel.

Got turned into this oil by a master mechanic for Detroit Marine Diesel engines. I have never used anything else in my duramax and recommend it to anyone that doesn’t have a DPF. I use oil analysis and the results wish for themselves.

This oil has a TBN of 12 and it's all I use in my Duramax LBZ trucks. Has a higher ash content not suitable for DPF trucks. Read the Amsoil article about the million mile Duramax.

I’ve been using the HD Diesel & Marine oil in my 2002 2500 Dodge Cummins, which is a flat tappet cam follower system. I trust the high zinc and other additives that are used in the older CG-4 & plus classification oils and Amsoil is at the top in quality. I don’t trust the “backwards compatible” statement in the use of the newer CK classification. These newer engines with DPF’s have to run the CK classification due to the ash from what oil gets by the rings and gets burned in the combustion cycle. The older high zinc and calcium additives cause problems in the current diesel emissions system, but you have to understand, these newer diesel engines are engineered for these oils. They are all running roller cam followers & roller tappets with less friction than my older flat tappet & cam follower cummins. I’m so thankful that Amsoil still offers the 15w-40 HD Diesel & Marine oil.

Very good quality

I have used this motor oil in a 2001 Ford F250. I have pulled a 38 foot fifth wheel among other things and it has never used a drop of oil. I change it once a year and I have been very impressed with the results.

great service and great product. don't use anything but amsoil

Good quality,recommended

i did a full fluid flush being , front diff , engine oil , transmission, t case , rear diff . the fluid quality is out standing as for the truck now runs and rolls like new and much more quiet as before. it’s clearly more happy that it was now that all fluids are done. the g56 manual trans shifts like new now and it’s got 140k on it . highly highly recommend AMS oil. i need to do a coolant flush next so if they sell coolant i will be buying it soon. 10/10 stars

First time changing the oil on my new to me 2003 F250 xlt 6.0L. was recommended the marine oil for the additives. We shall see

Using their product from front to the rear of my truck. 265,000 and still going strong.

I am running with this oil since 2007. Caterpillar 3406E. Oil changes are way over 60K miles. Do I need to say more?

Have always ran Rotella or the Polaris brand oil in our Polaris Ranger Diesel. Made the switch and immediately the motor is far quieter than it has ever been. Seems to stay cleaner as well

Best oil you can buy.

I have been using this oil in my Ford 7.3 for 15 yrs without a single problem. I change oil and filter every 10,000mi.

Very good quality

Good price excellent product

My 04 , 5.9 cummins loves this stuff.

Excellent Oil. Have used it for years in my Duramax