El Oso Road Professional Review and Guide
"For the most part, this long trail is suitable for passenger vehicles in dry weather. However, there is one section, a 0.5-milelong stretch immediately east of the Mud Springs Trailhead, for which high-clearance vehicles, preferably 4WDs, are required. The day the trail was surveyed there was a VW Beetle abandoned on this stretch of trail. The unfortunate vehicle suffered major damage to its undercarriage and was hopelessly stuck on the embedded rocks.
The driver was lucky enough to catch a ride with a passing vehicle, but only after he had spent the night along the trail. Special Attractions: Very scenic ridgeline trail with excellent primitive camping spots; Remains of the El Oso and Jolene Mines; Optional 7-rated detour. High-clearance 4WDs are preferred, but any high-clearance vehicle is acceptable. Expect a rough road surface; mud and sand are possible but will be easily passable. You may encounter rocks up to 6 inches in diameter, a loose road surface, and shelf roads, though these will be wide enough for passing or will have adequate pull-offs."