I suppose renting a motorcycle is out of the question?

I've seen a lot of great suggestions, I've toured a whole lot of California on my bike, but at that point, the ride is more what it's about more than the destination. Stop and take a pic here and there, otherwise just enjoy the twisty roads and scenery.
Yosemite in August will be crowded. Really crowded. Death Valley won't be as crowded

Death Valley is one of my favorite places, but not in August.
If you go over the Sierra through Yosemite on 120 to 395, there's Mono Lake, then south on 395 to Mammoth isn't too bad. Also going down 395 south, there are some spur roads that will take you up into the mountains and tend to end at a lake. South to Bishop and White Mountain. You can go to the Bristlecone forest. Some of the oldest living things in the world, thousands of years old, twisted and gnarly from the harsh winds.
If you go North on 395, you could see Virginia Lakes, Bodie ghost town and up to Bridgeport.
Or just do a loop over one of the passes. Hwy 4 is my favorite, 108 is nice too and has a lane each direction the whole way.
From Sacramento to Yosemite, don't take the main highways, make your way over to Hwy 49 and cruise down through there to Hwy120, much more interesting.
That's a couple suggestions I hadn't already seen. If you're cool with the sights to be seen, you can't really go wrong in any direction.
Bristlecone tree and Lake Sabrina (will have more water for sure this year).
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