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.
Although most people still have the oil in their car changed every 3,000 miles, most experts suggest that synthetic oil only needs to be changed after 5,000 to 7,500 miles. However, some manufacturers list oil change intervals as high as 10,000 or even 15,000 miles when using synthetic oil.