My husband and I are going to Hawaii in February, and we want to drive to the summit of Mauna Kea. We've read that rental car companies won't allow their cars (even 4-wheel drives) to be driven on saddle road. Is that true? As independent travelers,we'd rather not go with a tour operator. Can we possibly drive a regular rental car as far as the visitors center & then hitch/buy a ride with a tour operator or another visitor?
Thanks for any advice!

Check Harper's rentals. We just did a family mountain biking trip to Mauna Kea and it was no problem. Pricey, though.

Here's their web site:

http://www.harpershawaii.com/

It's true that the rental car companies have a clause in the contract that says you won't drive the car on the saddle road. I've always rented a car on the BI, but went up to the summit (twice) with a tour company. There were two reasons: 1)the tour van has oxygen on board, and the air up at the top is extremely rarefied (60% available oxygen, which is significant). I found that I needed the oxygen. That's certainly not true of everybody, but I was glad it was there. They also have parkas on board and it was very cold up at the top. Without the parka, I wouldn't have been dressed warmly enough. 2)The tour van operator had a telescope in the van and we spent more than an hour stargazing in the parking lot at the visitors' centre. The group I went with was small, only about 5 or 6 people, and although I generally avoid these things I found this one quite tolerable. The driver was knowledgeable about the things that we saw and the areas we drove through, and it seemed to me that he added to the experience. Have a wonderful time!

While true that all of the national car rental firms have a "no Saddle Road clause", we have always (at least 8 or 9 trips to the Big Island) driven the Saddle Road without difficulty...it's as safe and non-rugged as main highways. There's no reason not to do the Saddle Road. However, we've only been to the top of Mauna Kea once on our last trip. We decided to rent a four wheel drive vehicle for the day and I was sharing the costs with two other parties. When the person who left to pick up the rental returned to the condo, to my surprise he had rented a two-wheel drive, low-powered Kia...he is young and adventurous...on that particular afternoon and evening, even the Kia was just fine as the road was dry...just a few nights later there was snow and ice on the road and that Kia or probably any two wheel drive vehicle would not have made it and to have attempted the journey would have definitely resulted in a mishap which would have unavoidably let the rental company know that the contract had been violated.