Originally Posted By: silverbar
Delo 15W40 in the West.
You're correct. I've pulled their trailers, and out of curiosity, I've asked a few of their shop mechanics.
And for those interested:
FedEx: Rotella
Old Dominion: West of the Mississippi, Delvac Super 1300. East of the Mississippi, Castrol.
And from what I've gathered, - and as already posted, big fleets choose the brand of oil they use based on lowest price. Which makes sense, as all of the major brands roughly meet the same specifications.