Hiway 166 Bakersfields to Santa Marie?

We’ve driven this hiway many times over the past 10 plus years in a 39 foot motor home. Length of coach does not need to be a consideration Pretty good road, but two lanes , hills, curves, . Very scenic but let navigator or passengers do the looking. You keep your eyes on the road.

If you are not in a hurry, it isn't a bad route. Mostly a two-lane road with some sections of moderate curves. Lots of trucks use this route. A bit of climbing after leaving Maricopa. The most curvy sections are between New Cuyama and US-101. We drove the route both ways many times in a 27 ft Class C towing a Jeep Wrangler. We haven't yet driven it with our 39' DP towing a Jeep GC, but wouldn't have a concern. The biggest concern are other drivers in too much of a hurry. The next alternative I'd recommend is north on I5->CA46->US101 at Paso Robles and then south to Santa Maria. But that is quite a bit further. I wouldn't recommend CA58 in that size rig as it is very curvy.

No problem. 2.5 to 3 hours. Typical California coastal range highway. Scenery gets better the closer you get to Santa Maria.