I had my brother drive our almost 10 year old Toyota Corolla S economy car with 120,000 miles on the odometer up to the Mauna Kea Volcano Summit to check out the observatories and the telescopes.
There were warning signs at the visitor center ("VIS") that warned about the need for 4WD (four wheel drive or all wheel drive) but we had no problems going up or coming down.
My brother drove very slow on the way up in "L" low gear. We stopped a few times to admire the view and let the transmission cool down just in case it was over heating.
Then on the way back down we stopped several times at the parking lots to check the temperature of the rotors and brake calipers to make sure they didn't overheat.
Before we left the visitor center, we talked to some guys who drove a 2014 Hyundai Elantra sedan rental economy car who said that it wasn't too rough and just to take it slow both ways.
We saw lots of Jeep Wrangler rentals and other 4WD / AWD rental cars going up and down which you really don't need if you are a sensible and cautious driver.
Although this was a very dry and warm day with no rain. If it was raining or snowing and there was mud on the gravel road, we would not have attempted this expedition.
Please, if you have any doubts, do not attempt to drive up this road.
The entire driving time of these video clips was about 90 minutes (1 hour and a half). I sped up the driving parts by 1,200%.