Royal Purple04154 15W40 Oil, 1 Gallon (128 Ounces)

I have used RP, Shell Rotella T6, and Valvoline Syntech (both semi and full synthetic), Valvoline Premium Blue and conventional dealership oil in my last 2 Cummins. The RP seems to do a pretty good job. No excessive valve noise, doesn't seem to burn off, good pressure at idle and higher RPM's (based on the RAM calculated oil pressure gauge) and runs about as cool as the Shell Rotella T-6 (190-201 F. at operating temp). I probably won't buy again though. For the price I think I am going to go Amsoil HD kit which is 12 quarts plus a filter for about $200 U.S. dollars. I'm going to try Amsoil at my next oil change. However, I have no complaints about the RP.

I have been using this oil in my vehicles since 2012. I took my truck to the shop for a tune-up, and the mechanic recommended this oil, telling me how great it was. At first, I thought he was just trying to upsell me, but I decided to give it a try. I reset my fuel mileage to monitor the effects of the new oil. Sure enough, I started getting three more miles per gallon. I was convinced and have been using it ever since.

Used this oil in my 2005 Duramax, little pricy but well worth the price in my opinion

This stuff is the best. I put a lot of miles on my vehicles never had an issue. Try it you won’t use anything else.

I have been using this oil for 12 years. Engine runs smooth and the oil pressure and temperature in the normal range. I tow a 5000 lb boat and a loaded 10,000 lb trailer with no problems. You can't go wrong with this oil !!

The price is right but the container is too hard to handle. We used a funnel with 2 people but we couldn't tell how mush we were putting in the engine. We had to check it 10 times, also we spilled about 8 onces on the ground and a small amount on the engine. This would work best it I had 20 quart Mason jars and filled them all at the same time. Somewhere I have a pour spout that fits onto a mason jar. If I could only find it.

My son and I use these in all our trucks. When he rebuilt one of his engines, there was little wear and tear above normal for 240,000 miles. There was hardly any carbon buildup at all. So we will continue to use this in our diesel vehicles And you cannot beat the price here on Amazon. They deliver right to your front door and all you have to do is go out drain your oil put in a new filter and fill it up and you’re ready to go for another 7500 to 15,000 miles depending on your preference

Been using Royal purple for about 6 years without any issues