That is old Rotella in there, seen by the combination of normal KV100 13.37 with low flashpoint (fuel dilution), which tells us fuel lowered the viscosity but oxidation took it right back up. Oxidation is a sign an oil has been in a long time. Good news is the low Insolubles of 0.1 is quite good, and iron at 18 ppm is still not bad. Doubt this is going to be a real problem, its rugged Rotella after all.
I'd use Castrol 0w40 at walmart in 5 quart jugs bargain priced. Great oil. Plenty thick enough for this.