Valvoline Premium Blue (15W40). Taken from the Cummins website:
"Recommended for all Cummins diesel engines, also suitable for other engines.
Premium Blue Engine Oil is the result of Valvoline teaming up with Cummins to develop the highest standards in diesel engine lubrication. Working together, sharing technology and product development at every level, Valvoline and Cummins have taken quality engine lubrication to a new level. Premium Blue is formulated to provide advanced performance in modern, low emission diesel engines including the latest emission certified engines as well as Euro1/Euro2, operating under a wide variety of service conditions. Premium Blue is endorsed and recommended by Cummins, and is an approved *CES20071 engine oil."
There is also a 5W40 synthetic version.
"Recommended for all Cummins diesel engines, also suitable for other engines.
Premium Blue Engine Oil is the result of Valvoline teaming up with Cummins to develop the highest standards in diesel engine lubrication. Working together, sharing technology and product development at every level, Valvoline and Cummins have taken quality engine lubrication to a new level. Premium Blue is formulated to provide advanced performance in modern, low emission diesel engines including the latest emission certified engines as well as Euro1/Euro2, operating under a wide variety of service conditions. Premium Blue is endorsed and recommended by Cummins, and is an approved *CES20071 engine oil."
There is also a 5W40 synthetic version.