The load is the first of three that a Hillsboro company specializing in jumbo shipments is expected to haul through Oregon, Idaho and Montana on its way to Alberta.
The 901,000-pound load is for a water purification system described as vital to the oil extraction project.
It was supposed to leave the Port of Umatilla along the Columbia River on Sunday night, but "the equipment took longer than expected to load up," said Holly Zander, spokeswoman for Omega Morgan.
The load and transport vehicle are about 380 feet long, 23 feet wide and 19 feet high, according to the state Department of Transportation.
The height precludes travel on Interstate 84, except for a short stretch near Pendleton where it will use on- and off-ramps to get around overpasses, the agency said.
Oregon rules allow the megaload to move only after dark, and for no more than 8 hours a night. Crews will block two-lane highways, and the transport must pull over every five to seven miles if traffic needs to get by. The transportation department said vehicles could expect delays of to 20 minutes.
The route planned through Eastern Oregon is about 315 miles. Much of it is on Highways 395 and 26 in some of the most sparsely populated areas of the state.
About 20 protesters gathered at the port north of Hermiston on Sunday night to decry the shipment to a project that environmentalists have criticized for adding to greenhouse gases and aggravating global warming, the East Oregonian newspaper reported.
The company hauled one load of the refinery equipment across U.S. Highway 12 earlier this year, but a federal judge stopped a second load from crossing tribal and environmentally sensitive lands.