I don't know much about M1 TDT, but Delvac 1 has several heavy duty approvals. Maybe M1 TDT has been updated with more approvals, but the last I saw, it was limted to CJ-4, E7 and met Cat ECF requirements. D1 is CK-4, E9 and has the heavy duty specs listed. I'm sure that there are others much more informed about the M1 than me.
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