Spec for a diesel is 5W-40 or 15W-40. 10W-30 is not heavy enough to properly protect the engine in high operating temperatures. So its your engine but I wouldn't chance it running oil for a gasoline engine. If your wanting easier starting in winter go with a full synthetic 5W-40, and I will never run rotella

 

It's not oil for a gasoline engine. It's rated for diesel engines. Here is a link to the oil I'm talking about
Shell/Rotella T5 synthetic blend engine oil SAE 10W-30 1 gal. 550019908 at AutoZone.com

 

Good link

 

The 10w-30 tells us the weight of the oil, it can say whatever it may like. And we do not need to change your mind, just giving you some opinions. Am I wrong to say you joined the forum to teach everyone else? Or did you come here to help where you can and learn more than you know now. I know I am always learning. If you would not like to take the advice it is alright, we will also help you if/when you need to replace engine components. The truck is a heui system designed to be run on a certain viscosity oil. That is like saying that you are switching to power steering fluid for your transmission

 

I'm not arguing and I am here to learn, as I said I'm new to diesels, I'm just curious as to what damage it would do to the motor as it is a diesel rated motor and says it can replace 15 40 oil in colder temps. I've also been reading a few reviews about people who have run it in their trucks and say they have no problems with it. If I were using my truck for towing I would stick with the 15 40 but I was just curious to see how this oil performs. It also says that it meets CH-J standards

 

You should be particularly picky when it comes to oil, like I said your injection system is designed for 15w-40, although 5w-40 will work fine as well. Understanding the numbers will help you understand what the differences in the oils are. Viscosity is the oil's resistance to flow or, for the layman, an oil's speed of flow as measured through a device known as a viscometer. If an oil says 15 W – 40, that means at 210°F the oil will have a viscosity scaling of 40. The 15 W stands for this viscosity qualities at a colder temperature. The numbers may not make sense due to the fact that at different temperatures they are scaled differently. When switching to a 30 weight oil you are actually using a thinner oil. A thinner oil can not lubricate major engine components as well as a thicker oil. In extreme cold temperatures a 5W 40 is actually somewhat better to use due to the fact that oil will get throughout the system faster because it is thinner while cold compared to a 15w-40. The downfall of a 10W-30 oil in a diesel engine especially a power stroke is when at 210°F it is thinner then recommended to run possibly creating The opportunity to damage engine components

 

Ok I see what your saying. I've also been doing research and there have been other forums that say the 7.3 and 6.0 engines thin 15w 40 down to 30 over time. Is there validity to that?

 

I do not personally test oils nor produce them. But I can say that over time oil can deteriorate and break down. Would that happen between oil change intervals? I strongly doubt it.

Let me put it this way, I have had trucks come to my shop from the auction, purchased as a non running truck (no start). Icp was low, change the oil and they start and run perfect.

So if there is truth from a sae 40 breaking down to a 30, why would you want to start at a 30?

 

Full synthetic 5w-40 or Motorcraft 15w-40 is all I would run in a 7.3

 

A 7.3 or a 6.0 breaks a 40 down to a 30, but the people who have run the 10 30 and have had their oil tested says it doesn't thin it down so I'm not sure