Customer Ratings & Reviews

My mileage increased a bit. The engine runs a lot smother. I plan on keeping my truck for many years and this oil is go to oil.

Dumped class 3 synthetic rosella t6 for a true synthetic class 4 PAO Amsoil Sig Series 5w-40. Turbo Diesel is running smoother, quieter, cooler and 2-3 mpg boost! Worth the money!

I was a Royal Purple junkie since it was the only synthetic available to me where I live and got it free. It worked great in my gas truck and other gas vehicles. I switched to Amsoil since I purchased a diesel truck and became a Preferred Customer. Really like that part !!! The truck runs much better and accelerates better than the Ford oils that were in it and oil change at 25,000 miles is a nice $$ saving feature. I will switch to the new synthetic 5-40 on the next oil change and then extended changes past 25,000 would be nice. I monitor all things done to my truck and log it. Put 9,000 mikes on the truck in less than 4 months and excellent results !!!

Best lube oil for my one ton Ram 3500. But not without the Amsoil EA filter.

I use 15 40 in any vehicle I have which includes my tractors, lawn mowers.

I drive a lot of miles in a short period of time and I don't have time to change oil every 5 to 6ooo miles

Perfect product

I've been using AMSOIL heavy duty diesel oil for years and it has performed extremely well. This year I decided to try the Signature Series Max-Duty and was I amazed. I didn't believe I could tell the difference but the engine runs even smoother. I tow trailers with my truck and protecting the engine is paramount to reduce wear and lengthen the life and this oil delivers.

For my Duramax diesel

You can't go wrong with the best of oil produced on the planet Peace of mind means everything and Amsoil gives you that peace of mind

I use this oil in my skid loaders as well as heavy duty pickups pulling heavy loads daily. I have been sold for many years after I had 6.0 diesel that dumped all the oil and the only thing that saved the motor was this product. All the shop had to replace was head gaskets

Use this in my 2015 super duty 1 ton dully. A do a lot of heavy towing long distances

In my Excursion Diesel 250,000 miles

First, I'll say that I love Amsoil. I run Amsoil in every engine/transmission/differential/etc I own. I'm not sure about this new oil. My oil temp in a Ford 6.7 Powerstroke usually runs about 203 degrees (previous version of Amsoil diesel oil). With this new oil (December it might have come out???) I'm running 7-10 degrees hotter on average. I'll probably try one more oil change with it and if it still runs hotter, I'll have to find another brand.

I am astonished at the engine oil life provided by this oil, compared to the Mobil synthetic I used previously. I'm at 14000 km, 80% city, and the computer is telling me I still have 20% oil life. Previously I would get to about 10k and be looking to change. Admittedly I changed to Wix filter at the same time from Oem, so not a 100 % true comparison. Winter, with more idling, will be the real test. Engine seems to be running cooler even in 30C weather- that's hot for us!

I have a 2011 Chevy one ton dually long bed . Now over 100,000 miles and is running great I feel because I have used Amsoil since day one . I have used every brand with prior vehicles and always go back to Amsoil.

Use it a 09 Chevy Duramax, starts great even if it hits 0 or below

Buy diesel, gas oil plus PI for my gas vehicles. Amsoils is the best!

I currently use this product on my 2016 Ram EcoDiesel with no issues and have use the previous 5W40 diesel product on previous diesel pick up trucks and heavy-duty equipment with no complaints. Thank you Amsoil.

I'm running the 15w-40 Amsoil Signature Diesel in my Corvair air cooled engine in my 22 foot RV. Very heavy duty use for a 3 liter engine from the '60's, and it performs perfectly, along with the Amsoil 75w90 Severe Gear in my differential, and Amsoil ATF in my Powerglide transmission. I use nothing but Amsoil products in my 17 Prius, the 16 Subaru Forester Turbo, And every car I have owned in the last 15 years, and will continue to do so.