With most rental cars giving you unlimited miles, I'm very much of the opinion that when you factor in mileage and wear and tear on the car plus vehicle depreciation due to the long miles on the road trip--that renting a car for long trips is the way to go.
Especially when compared to owning a second care with an ICE just for the occasional trip.
1. Flexibility. For a rental car you need to plan ahead, pick it up on time and return it on time. Traffic jam delaying you? too bad. You now pay a surcharge.
2. Cost: the rental cost is actually only a small portion of the cost. Extra insurance and other fees end up more than the rent itself.
Your car will depreciate regardless of that road-trip, just by virtue of time passing. Rental companies won't subsidize the wear and tear for you, so you have to pay that anyway.
I know a lot of women who own a beater and when they want to drive long distance rent a car. I think because they know it's cheaper and the idea of being stuck on the side of the highway makes them anxious.
And then there is my friend on a fixed income that's realized it's cheaper to rent a compact car for long drives. Same as above because having the car break down in nowheres is expensive quick.
I actually like my car and have a bunch of my stuff in it. Renting another car just to save a few dollars on a road trip is ridiculous. Plus when I show up at the rental agency they often don't even have the car that I reserved. Now what?
Especially when compared to owning a second care with an ICE just for the occasional trip.