1999 Ford Taurus Owner Guide 1st Printing - Page 115

Driving fourth gear will increase your fuel economy when you travel at cruising speeds. Overdrive may not be appropriate for certain terrains. If the transaxle shifts back and forth between third and fourth gears while you are driving hilly roads or if your vehicle requires additional power for climbing hills, shift into D (Drive). When to use D (Drive) The D (Drive) position eliminates the needless shifting back and forth between third and fourth gears that your vehicle may do when driving on hilly terrain. It also gives more engine braking than overdrive to slow your vehicle on downgrades. 1 (First) Use 1 (First) for when added engine braking is desired when descending steep hills. The automatic transaxle will shift to the proper gear to ascend any grade without any need to shift to 1 (First). P R N D D 1 P R N D D 1 Do not go faster than 61 km/h (38 mph) when in this gear. You can upshift from 1 (First) to overdrive at any time. 115