Before this big, bad pickup arrived, manufacturers largely used upgraded versions of their light-duty trucks to handle heavy-duty work. The 1999 Super Duty was a separate model line with its own style and hardware underneath.
You can run a conventional oil 5K miles but you should be able to run a synthetic oil 7500 to 10000 miles. Royal Purple API-licensed synthetic engine oils allow motorists to travel as many as 12,000 miles as the recommended oil change interval.
1 Only Toyota vehicles in which 0w-20 synthetic oil is required (except for the 2TR-FE and 3UR-FBE Engines*) have been approved for extended oil change intervals of 10,000-miles/12-months. ( 2 However, you should continue to check the oil level regularly and top off if needed.