[Iexpedite]

I took a trip recently to Ohio in my 14 Elantra. During my drive I encountered miles of rolling hills. When I hit the hills my transmission would downshift to maintain my cruise control set speed. Every downshift met with a significant reduction in fuel economy on my ScanGuage. I decided I would shift into manual mode to see if there was anything to be gained by locking the car into high gear.

My car would not upshift to a higher gear in manual mode while climbing so I tried it the opposite way. I climbed the hill locked into 6th gear. When my fuel economy settled I shifted into normal automatic mode which triggered a downshift to 5th gear, with each downshift to 5th I lost 4 MPG.

I guess I'm wondering if anyone else has experience with locking in high gear? Does the car normally shift down to protect the weaker 6th gear or is it done to ensure on-demand power is available.