I run synthetics in my vehicles. Although they cost more, I usually run the 5K-10K. It depends if the vehicle is in warranty. I try not to run conventional oi over 3K. Still, conventional oil of today is very good. I like Havoline and Valvoline. I hear right now Havoline is the best in conventional oil. If you run mostly highway miles, then you can extend your oil changes. Probably best to get an oil analysis though. I've used Rotella in my Comanche. The local garage siad it was better than other oil and 4K on the changes. Also get a good filter, NAPA Gold, Purolator Pure One, Baldwin and WIX are good. The Mobil 1 is suppose to be the best, but expensive at $10.
Tom