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.
Originally Posted by bigmac8675. Synthetic oil can last longer than regular motor oil.... at the most twice as long. (6000 miles compared to 3000 miles) Although if you baby your car or have a high performance car you should still change it between 3000-3500 miles even if it is synthetic.