I change the oil in my H3, the wife's Tahoe, and my commuter (Toyota Tercel) every 5,000 miles with standard Dino oil (Quaker State). Been doing that for over 40 years, and every vehicle I've ever owned has gone well over 250,000 miles, although I've started to put the Quaker State High Mileage (synthetic blend) in them lately. The only one I always run full synthetic (Mobil1) in is my RV ('04 class A on a Workhorse chassis, 8.1 V8). I figure that one gets alot more abuse simply because of the weight that it's hauling around, so I spend the extra, but it's also still low mileage so the "high mileage" oil is a moot point there. Some newer cars actually require full synthetic; my daughter's '15 Corolla uses synthetic 0W-20, but allows for 10,000mi changes.