I look at it like this: If you have to push harder on the gas in D, then you are wasting gas. If you maintain throttle level and drop a gear, then you are wasting gas. Either way, you waste gas.

I have a 380sel in a rather hilly part of Arkansas. If you dont shift manually, you will watch that econ guage stay all the way in the red until you get on a flat at about 40mph. It will be less red if you manually shift it. It doesnt have the low and mid-range torque to handle the terrain in town in 3rd and 4th. Now if I was in Iowa or Minnesota, I could keep it in D until I wanted to have some fun without a problem.

Drive your car according to the terrain. Guage the terrain by your car.

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