Jake brake on or off driving on flats or small hills?

Holstein, you're from FLORIDA! Our freeway overpasses are HIGHER than your highest "mountain/hill".....:B

That said, like Ivylog, many, not all, Monaco products have a foot switch for the engine/exhaust brake. I think they are a big plus. I have a two stage engine brake with the foot pedal. On small hills and flats, I usually leave the switch on LOW which activates only three cylinders and on bigger hills/mountains, I switch over to the HIGH witch activates all six...YMMV...Dennis