Cummins ISL Oil recommendation

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

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.

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.

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.

wolfe10 wrote:
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.

Brett, is, of course, correct. The spec too look for is CJ4 and the two called out meet that spec.

It looks Like Speedco offers Rotella T and Baldwin Filters for $299, so is that Rotella T1 most likely as the standard oil?

My motor gets Valvoline Blue. If its good enough for the Cummins factory to use, its good enough for me. I change my own oil so its cheap enough to go with the good stuff.

Seems to me you can't go wrong with any Diesel oil, just how much do you want to spend.

Delo LE 15-40W is the best oil for your Cummins. It has all the good additives including moly that other diesel oils do not have. In all my oil analysis it held up the best.

Have always used Rotella 15-40. Never tried any others!