I had a 2 week construction job midway between Santa Maria and the I-5. I traveled Hwy 166 in both directions many times during those two weeks.
It seems a lot longer drive than it should. There is a town mid way New Cuyama it's mostly dead but there is a diner and store. I can't remember if there was a gas station. I do remember stopping at a station just before the turn towards Maricopa.
Like others have said typical two lane country road with many blind intersections so keep your eyes open. As you get to Maricopa you need to pay attention to the signs for HWY 166 as you travel towards I-5. It becomes a main city street.