We had a Sebring convertible from National in May. We drove to the 9,000 foot elevation to the visitors station. All i can say, WHAT A DOG THIS CAR WAS! I did not know it at the time but it was a four cylinder. I know how to drive a car and this one couldn't pull the hill in any gear. We tried up shifting, down shifting, using our feet like the Flintstones, etc Just would not go. That said, no problems anywhere else on the island with this car and we hit every highway on the island, obviously inclusive of Saddle Road. We have done Haleakala many times with rentals and never had a problem climbing or descending like we did with this car.

My biggest thing regarding Mauna Kea using a standard rental car is if you break down, it will cost a ton of money for the tow. If four wheel drive is recommended for any reason, then maybe people should use it. Also, nothing says you can't rent a four wheel drive for one day.