Here's the original oil specs for that unit. Diesel Engine oil is detergent type and it has the full flow oil filters that are associated with detergent oils. The only thing I'd change is TDTO for the oil clutch. Modern oils are deemed to slippery for clutch applications.
Multi-grade oils have a high percentage of polymers that change the viscosity with temperature but they do nothing for lubrication other than this feature.
Bearings on these units are high clearance and are better off with the higher viscosity oils unless your dealing with very low temperatures. Older well worn units can take advantage of running the SAE40 in mild climates and is probably closer to the original SAE30 mineral based oils.
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Also attached is a list of Chevron products for Caterpillar.