If you use Rotella 15w-40, your oil turns deep black in the first 500 miles. If you use AMSOIL 15w-40, I am still waiting for oil breakdown. So far, 1500 miles. The oil looks like the same oil as I put in at 424k mile oil change interval. Rotella probably isn’t what you have been told. If you want a PSD 7.3L to work the way it was designed, use better oil. Try AMSOIL. It is the best.
Just a great product, this diesel oil was a noticeable difference in running cleaner then OE motorcraft
Bottom Line
Yes, I would recommend this to a friend.
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5 star rating
Because it works
By 
TROY, 
a 
Verified Buyer 
on 
January 26, 2026
This is my go to oil for my 2015 F250 6.7 Powerstroke. I do this every 5,000 miles because I love my truck. I take care of it and it takes care of me!
Bottom Line
Yes, I would recommend this to a friend.
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5 star rating
Best lubricant on the market.
By 
JEFF, 
a 
Verified Buyer 
from 
North Carolina  
on 
January 21, 2026
I’ve done a lot of research using independent lab research and reviews about AMSOIL. In my opinion and by the information I have found, I have come to the conclusions
that AMSOIL is the best money can buy.
Had a snow contract in this area.
Worked the 6.4 diesel hard and non stop switching drivers. 24 hr work
The engine smooth and as quiet as a diesel can be.
No consumption in 2 weeks. Many hard km. Great product
I love this oil paired with Wix filter gives me confidence my engine is in good hands.
Bottom Line
Yes, I would recommend this to a friend.
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5 star rating
Good stuff
By 
BOGDAN, 
a 
Verified Buyer 
on 
November 29, 2025
I’m using the oil in my semi truck 10w-30 ful synthetic, it’s a good stuff
Bottom Line
Yes, I would recommend this to a friend.
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5 star rating
The best oil on the market hands down
By 
EMMETT, 
a 
Verified Buyer 
on 
November 28, 2025
Since using AMSOIL for my diesel has better gas mileage. That tells me everything I need to know about this oil compared to the part store brand. AMSOIL is the only oil I’m using in my diesel from now on
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