Yes, and this is the one island where there is no interesting version of the question. Hawaiʻi Island is about 4,000 square miles, larger than every other Hawaiian island combined, and the things people come for are scattered across all of it.
The Hele-On bus exists and serves residents between the main towns. It is not a way to see the island.
Distance is the whole story here
Kona to Hawaiʻi Volcanoes National Park is roughly two to two and a half hours each way on the southern highway. Hilo to the same park is about an hour. Kona to Waipiʻo valley lookout is around an hour and a half. Crossing between Kona and Hilo on Saddle Road takes about ninety minutes.
Those numbers are the reason a Big Island week gets planned around drive times rather than around a list of sights, and the reason a badly chosen base costs you a day of it.
Fly into one airport, out of the other
Kona (KOA) sits on the dry west side, Hilo (ITO) on the wet east. An open-jaw booking into one and out of the other removes a two-hour backtrack at the end of the trip and lets you sleep near the volcano without doubling back.
Rental companies will do this, and one-way drop fees between KOA and ITO are usually modest or waived. Check before you book rather than assuming, because it varies by company and season.
Saddle Road and Mauna Kea, which are not the same thing
These get conflated constantly and the distinction matters for your contract.
Saddle Road, now the Daniel K. Inouye Highway, is a fully paved modern state highway between Kona and Hilo. Old rental agreements banned it and a few outdated blog posts still repeat that. Current conditions and closures are on the state highways site.
The Mauna Kea summit road above the Visitor Information Station is a different proposition: steep, partly unpaved, at nearly 14,000 feet, and genuinely requiring four-wheel drive. Most rental contracts prohibit it outright, which means no coverage at all if something happens. The visitor station itself, at 9,200 feet, is reachable in a normal car and is where the stargazing happens anyway.
Volcanoes, and why the timing matters
Hawaiʻi Volcanoes National Park is open around the clock and the crater after dark is a different experience from the crater at noon. That is only practical with your own car, and it is much more practical if you are sleeping in Volcano village rather than driving back to Kona at midnight.
Eruption status changes and closures follow it, so check the park's own page close to your visit rather than trusting anything written months earlier, including this.
Booking
Kona has the larger fleet of the two airports, so if you are flying in and out of Hilo it is worth checking both before you commit. Book refundable early and re-check, the same as everywhere else in the state.
On the drives themselves, the south coast run and the Kohala backcountry pass a great deal of unmarked history and geology. An audio tour that explains what you are looking at makes the long stretches the point rather than the price.
