15w40 looks like its similar to the Rotella T. Its a diesel oil, its on sale for 9.50 a gallon. Any one ever use it?? I use Mobil one, but im willing to use this for break in if its decent.

Delo 400 is Chevron's competing product to Shell's Rottela. THEY ARE EXTREMELY similar, and both are very good oils. They are completly substitutable for appropriate applications. Both high deteregent diesel ois of course, and if your're ok with the detergent level then go for it. There is some evidence that it works against the lubrication effects of zinc (I am not convinced thats really a significant issue) and other evidence that detergents alter the surface tension of the oil causing it to draw to itself and therefore run off of vertical surfaces more than other oils. Picture cam lobes on an engine that sits for weeks. (not convinced thats a big issue either, but just stating information I have seen in reports--maybe true maybe not???)
But back to Delo 400--quality stuff--ever Kenworth and Peterbilt in the world is factory filled with that oil (meaning Cummins and Caterpillar support the product too.)

I've ran it in my 10 sec. RR, and 9 sec. Challenger for years. Bearings have always looked good, I do run roller cams btw. Also is the only oil my 2004.5 Cummins Dodge has seen.

I run it in my car for start-up and race with it. I also run it in my cummins.