Break-in is generally referred to as the first 1000 to 3000 miles. Your owner's manual will have information on break-in, and the FEH manual does mention something about not driving at constant speeds for the first 1000 miles or so. I don't know if you've found the Mariner Hybrid owner's manual online, but the vehicle's are so similar you might enjoy perusing the
'06 Ford Escape Hybrid owner's manual online.
I personally didn't do anything special in my Ford Escape Hybrid (purchased in March '06), and even took it on a all-highway road trip to Dallas and back home to San Antonio. On that road trip, I hit 1000 miles on the odometer at a stop light in Glen Rose, Texas, home of the famed dinosaur tracks... Glen Rose = Dinosaurs = Fossil Fuels. Fitting, no?
