Royal Purple 12154/300905 API-Licensed SAE 15W-40 High Performance Synthetic Motor Oil - 1 qt. (Case of 12)

Great oil, made my engine run smoother than before. Especially now that most of the diesel in my area is biodiesel, I purchase full synthetic oil to clean up the dirty burn up in the cylinders and the additives in this particular one help make sure the oil stays clean for longer.Only downside about purchasing 5 gallons is there isn't any markings to help you measure how much you have put in.To speed up the oil changes, I also have bought 3 gallon containers of this which gives you 12 quarts + 3 individual quart containers. Anytime you buy the 5 Gallon, fill the other containers and when it comes time for oil change you have a accurate way to measure how much you putting in.

Use this oil in my Owens 2.8 Gasoline RV generator. I wanted a syn oil in the weight recommended by Owens. Their oil is all most twice the price and it's unclear whether it's syn oil or not. She seams to run smoother and quitter too.

I use this in a boat and run about 50 to 70 hours a year on the boat and I change the oil every other year. It has worked perfectly. I have over 700 hours on my engine with no issues. I highly recommend this product.

This is the best oil they make as far as I am concerned. I run in my cummins for 20,000 miles and have K&N oil filter. The oil test still shows I can go further but I will keep changing at 20,000. I have ran other name brand oils and it failed test at 10 and 15000 miles.

Royal Purple 15w-40 is a great full synthetic oil. I tow a 10,000 pound travel trailer with my Ram 3500 6.7 Cummins TD. No more tapping noise as my torque increases to pull a steep grade. My Cummins loves this oil, as do I. It's Royal Purple Duralec for my investment. I have since changed my mind about the value of this oil. There is now the Mobil Delvac Extreme full Synthetic as well as Shell Rotella full Synthetic both are 15W40 diesel oils. Labs return the same results for a much lower price point.

This might be the worst item in the history of Amazon to return. Forget the fact that there's a 40.00 charge for the return. No UPS store will accept it. When I attempted to go to a main location. They wouldn't accept Amazon return label. Now I'm stuck waiting for someone to cine pick it up. Will not be buying this again.

Great Product! I have used RP oil in my diesel for the past 3-4 years with NO issues. Please update your post to include The CK-4 rating covers CJ-4 and CI-4 applications. Overall highly satisfied.

After my oil change from DELO oil to the royal purple, my Kubota tractor runs so much better. I wont use anything else from here on out.

As advertised

Excellent oil, my tractor loves it