Cummins ISL Oil recommendation

20 years ago I researched this at a shop that rebuilt million mile truck engines. They said that engines using Dell 400 were amazingly clean and those using Shell Rotello T had a slight amount of buildup. Since I often let my heavy equipment sit for extended periods I went with Shell R T in the hopes the buildup would help protect the engine from corrosion.

No way would I pay for synthetic if I changed the oil every year which I do not and I only use Shell RT which I change every 15,000 miles.

I love Supertech oil and they do sell Diesel oil. They are packaged either by mobil or shell. I've never had a problem using it and would suggest it to anybody. Much cheaper at walmart.

Many reasonable choices.

Shell Rotella T 15-40 and Delo 400 15-40 are popular choices and are available at Walmarts, etc.

You will not wear out that engine in an RV, so worrying about whether a special (read that expensive) oil extends engine life from 800,000 miles to 1 million miles is not really relevant.

If you have some special circumstance such as pulling a 10,000 pound trailer through the mountains in the summer, that may warrant other considerations.

Valvoline Premium Diesel oil is what Cummins recomends for my ISL.