Actually, most oaks tend to be fairly sensitive to ester triclopyr (Remedy's active-ingredient). But, when conducting basal-bark applications on larger trees (>4-6") - and especially if they have thicker/rough bark - one should inflict downward-angled cuts spaced evenly every 2" around the tree's perimeter and near the base (the "root crown") before making an application.
Without these cuts, the herbicide/oil mixture will have a more difficult time penetrating thicker layers of bark and reaching the underlying cambium layer - which contains the tree's vascular system.

Kelly Duffie
Cypress, TX