Answer:
User
Step-by-step explanation:
Buy center refers to a decision making center for purchases whereby all the parties involved and related to such a project are included in the decision making process.
A user refers to someone who has a right to enjoy a product or a service and derive satisfaction.
In the given case, the truck drivers represent the ultimate users since the trucks shall be in their possession and driven by them and it's they who shall see to it that the fuel tanks of such trucks don't run out of fuel.