Do you need a 4WD to get to the Mauna Kea summit? How difficult of a trip would it be with a 2WD? Thanks.

The final approach to the summit is unpaved and very, VERY steep, to the point where, when we made the excursion in a 4WD van, I was amazed we made it to the top without sliding.

While I wouldn't say it's impossible in a 2WD vehicle, it's definitely NOT recommended. Also, the summit is subject to snowfall during winter months (it was covered with snow just a few weeks ago when we were there) and that would definitely be the difference between making it and not making it.

And lastly, if it's a rental car you run the risk of pissing off the rental company. As far as I know, rental cars are prohibited on both the summit road and Saddle Road leading to Mauna Kea.

Definitely agree with the previous post. It's a rocky, incredibly steep climb, and very hard on cars especially because of the high altitude. Visibility is unpredictable - it can be gloriously clear one minute and blizzard conditions the next. Once you get above the weather it's very clear, but on the way up it can be treacherous.