Welcome to TBN.
Do not know about protiens the manufacturer, or thin oil burning the machine.....
I do know in older more used engines, be diesel or gas, a heavier oil may help an older engine not burn as much oil.
In warmer climates such as the mediterranean, a person could use a 20w-50 engine oil. Only thing is I do not know of an 20w-50 oil that is considered a "diesel" engine oil, with the right additives for soot control, a high tbn and other additives a diesel engine oil should have.
15w-40 is a good all-around oil. Its not overly heavy for gas engines but has the additives for a diesel.
I would use a quality 15w-40 engine oil.