First don't forget your oil filter. Use a good one. Napa Gold, Wix, Balwin (basically the same), Puralator Pure One are good choices. I'd check out Bob Is The Oil Guy website for more info. Also, if you do mainly Highway driving, then oil changes can be extended. Still, I'd suggest going 5K on oil changes on your new engine for warrany purposes. The cheap oils are probably today better than the premium oils of the 80's and early 90's. From what I've heard, even the cheap oils did well back then, you just had to change then at 2K, before the additives got used up. As far as aircraft engines, I think they usually run at a constant RPM. Thats like pure highway driving. Your engine will last a lot longer and a lot less stress on everything including oil. If I was running 80-90% highway miles, I'd consider running a good dino oil 5-7K over 3 months. Plus the worst for an engine is the short trips. Most of your wear is the startup. Also, if you don't run over 30 minutes, then the water isn't burned or boiled out of your oil. Synthetics are less hydroscopic than regular oils. I'm not knocking people who use conventional oils and change it reguarly. I just notice better performance with synthetics, and its worth the price to me. I justify the cost with extended oil change intervals. Hope this helps and enjoy your new jeep.