Okay, that's different. Death Valley itself, and most of the touristy sites are in the eastern part of the park, located near the Nevada border and is easiest accessed from there. It would be a very long day accessing that area from the west via 395. If you just want to 'touch base' inside the national park, you could head east from Olancha on 190 to Panamint Springs. Not much there, but you will pass the Father Crowley overlook, where you can watch the Navy fighter jets out of Lemoore or Fallon blast down 'Star Wars Canyon' below you @ 600+ mph. There's a lot of cool sand dunes in the park, Eureka being my fav...it's a washboard dirt road, as are many in the park. Take plenty of water, and most of the park does not have cell service. If you have mechanical problems, don't leave your car! Many folks die within a half mile of their vehicle when they 'went looking for help.'
Still recommend a drive on the June Lake Loop, it's about 30 miles north of Mammoth. The 'Whoa Nellie Deli' at the Mobil Station at the base of Tioga Pass a bit further north has good grub and often live music, but beware of the seagulls when eating outside - I lost a New York steak to one when i left the table to get pepper.