Customer Ratings & Reviews

I expected AMSOIL Signature Series 15W-40 100% Synthetic Max-Duty Diesel Oil to do well in my vehicle but I did not expect how much better than my usual Rotella T6 15W-40 it would do. I noticed right away fewer exhaust filter regeneration cycles that continue to get better to where I am almost at none and just maintaining a consistent level between 52% and 68%. I believe it took a while to fully get all the remaining Rotella oil out of the engine. After the second oil change using the Amsoil product it when I have been able to maintain exhaust filter percentage between the 52% and 68%. Fuel mileage has improved around 8-13%, along with a noticeable reduction in engine noise and improved power. Super pleased and will from now on only use the AMSOIL Signature Series 15W-40 100% Synthetic Max-Duty Diesel Oil in my 2021 GMC 3500HD Duramax.

So far working as claimed and truck seems to be more quite compared to using Rotella T6 5W-40 (winter) & Rotella T6 15W-40 (summer)

Very fast shipping and in perfect condition

Best diesel oil and automotive oil on the planet!

Great oil, great website, and fast shipping. Can't beat it.

I've been using Amsoil for a while. Their quality is really good and I'll keep using it.

I researched several brands of Full Synthetic Diesel Oil for use in my 2016 F350 with the 6.7 Powerstroke. The Signature Series was my choice because of all the results I read and reviews I watched. Its the best in my opinion for my driving style and the extra weight of my truck plus the over sized tires. I follow the severe duty maintenance schedule.

Runs better than shell rotella

This is the only motor oil I run in my 2007 6.0 Powerstroke; it runs amazing on it. Injectors fire beautifully, as they're run off high pressure oil in this motor. I know that I am putting the best quality oil in my truck when I use this product. I know many other people with the same generation of truck as mine, they're all running AMSOIL as well. Highly recommend.

I have used Amsoil for years and continue with my newer Cummins with roller lifters, 30,000 miles and no issues.

Highly recommend all of their diesel products! My Titan loves when these fluids are in her!!!

Nice oil

I use this product in my 2024 GMC 2500 duramax diesel. Great results, Great service. I have used this product in my 2013 duramax with the same results. Very satisfied.

I love this product! It keeps my Duramax running strong and it's absolutely doing its job. Keeps it smooth and at top performance.

my truck used to be a fleet truck at where i work. truck has used amsoil since new changed every 25k miles. engine has 0 blow by at almost 250k. The results speak for themselves! i now run amsoil in everything i own.

Can not say enough about this product and Amsoil. I am a little bias but swear by everything Amsoil. Always keeping my diesel properly lubricated all through the 10k oil changes.

excellent product

I will only use the signature series oil in my super duty. I’ve been using it for years now. Absolutely love it!

Excellent Service. Quick delivery on a great product

It has improved my oil pressure an reduce my engine noise