1996 Mercury Sable Owner's Manual - Page 149

NOTE: If your speed increases above your set speed while driving in j (Overdrive) on a downhill grade, you may want to shift to D (Drive) to reduce vehicle speed (or, turn j [Overdrive] off by depressing the O/D OFF switch on the gearshift lever). The speed control cannot reduce the vehicle speed if it goes above your set speed on a downhill grade. For the best fuel economy during normal driving conditions, leave the gearshift in j (Overdrive), or resume as soon as practical. RWARNING To keep control of your vehicle, do not use the speed control in heavy traffic or on roads that are winding, slippery, or unpaved. Accelerating With the Speed Control Operating You can use the accelerator pedal to speed up momentarily. When you take your foot off the accelerator, the vehicle will return to the set speed. NOTE: When driving in hilly terrain, at high altitudes, or when pulling a trailer, you may want to drive in D (Drive) (or turn j [Overdrive] off by depressing the O/D OFF switch). This will improve speed control performance. 122