Originally Posted by Hersbird
Best mpg potential when hot but without doing any harm. Also less expensive to purchase up front is better as well but not as important. I'm not looking for the cheapest but I'm also not going to spend Amsoil money either.
Run exactly what cummins recommends. Cummins engines, if you just go exactly by the book will go 500k+ without a problem. Going 500k or more miles will save you so much more money than experimenting with different oils just to see. You bought the right truck, just go by the book and change the oil right on time and the engine will last longer than the body sitting around it.
I've seen people pull a 300k mile Cummins out of a truck and put it in another truck and put another 100k on it and get 18mpg highway or more without any major trouble.
If you've got a 12V and your MPG sucks, you already know the answer to better MPG, and if you don't then just google "How to get better MPG 12v cummins" and read read read