Unless the oil has seen almost all city/idling/short trips (less efficient driving conditions) I'd run it. I've put T5 in a couple engines and it seemed to perform very well.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".