If you do a lot of stop and go driving, better to go with the severe duty schedule (5k/6months), otherwise the normal of 7.5k/6month schedule should be fine. Note that under the severe duty schedule, transmission fluid exchange interval is reduced from 150,000 miles to 30,000 miles.
Special Operating Conditions (severe duty schedule)
However, if one or more of the Special Operating Conditions outlined below better describes how you typically operate your vehicle, you will need to perform some maintenance services more often than the Normal Schedule recommends.
• Towing a trailer or carrying heavy loads
• Extensive idling and/or driving at low-speeds for long distances
• Driving in dusty conditions
• Off-road operation
• Use of E85 fuel 50% of the time or greater (flex fuel vehicles only)