Im new to the Cummins world but so far so good... I have a 98’ 12 valve with 113k miles. I bought this from a used dealer, so I really don’t know what kind of life it’s had. I know I’m the 3rd owner... I have an acquaintance that sells amsoil 15/40 and he runs it in his 18wheelers and swears by it... so I decided to put it in the 12 valve, says I can go 10k miles before changes... I have since bought a new 2019 2500 and have put 4400 miles on it so far... I plan on using amsoil for it as well... just seeing what most of you out there use in your Cummins....? I’m sure there’s a sales pitch to every product, but seems like the oil test are really good on the synthetic motor oils that I’ve seen.