1996 Ford Aerostar Owner's Manual - Page 210

RWARNING If you use the temporary spare tire continuously or do not follow these precautions, the tire could fail, causing you to lose control of the vehicle, possibly injuring yourself or others. RWARNING The tire size on the E-4WD must be maintained. Your vehicle may have a full diameter mini spare or a full size tire. This full diameter mini spare is special for the E-4WD and another mini spare from another vehicle can not be substituted without the possibility of damage to your vehicle. All tires should be inflated to the manufacturer's recommended pressures. RWARNING To avoid injury, never run the engine with one wheel off the ground, such as when changing a tire. Extended use of other than matching size spare tires on a Traction-Lok axle could result in a permanent reduction in effectiveness. This loss of effectiveness does not affect normal driving and should not be noticeable to the driver. 230