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.
SO im wondering about synthetic oil in my 2012 corolla and how many miles is safe to go over without changing it. You could change 100% synthetic oil at 6-9k miles and not have a problem (synthetic blends and regular dino oil at less mileage). This information is all over the Internet...