Just got back yesterday from another one of my insane one-day trips to see my son's soccer game. 500 miles roundtrip, arrive home about 1:30 a.m.

My choices are GENERALLY my 8-cylinder SUV, which I enjoy driving, but it's a 2009 with 178,000 miles on it, gets about 18mpg on the highway, and has no "safety" features in it like adaptive cruise control or lane assistance. Oh, and the manual says it *requires* premium fuel, not just recommended -- or rent a new car from Hertz.

So...all taxes included, out the door, $39 for a small car, like a Corolla. It's fine for my wife and I for one day trip like that.

Here's the math on it, too.

I generally get 35-40mph on their rental cars. I had a Prius a couple of weeks ago and got 54mpg, and I've received as low as 32 mpg, but generally it's 35-40mpg.

Let's say 36 mpg to make it easy.

So rather than buying 28 gallons of gas for my trip, I buy 14.
And rather than spending about $3.80 a gallon, I spend about $3.10 (in my area).

Gas cost alone:
My SUV: $3.80 * 28 = $106.40
Rental: $3.10 * 14 = $43.40

Gas savings: $106.40 - $43.40 = $63

I save $63 in gas, give them $39, they're paying me $24 to rent their car for a day. Not to mention another 500 miles on the tires, wear and tear on the engine, quicker oil changes, closer to the timing belt service, etc.

My car is more comfortable, sits up higher, etc. - but I do like the adaptive cruise control instead of my non-radar cruise especially when I'm driving home at midnight and after.

Driving close to 500 miles tomorrow, and will be taking my own car, so I don't always do it. But I have rented Hertz cars 10 times since August 22. A couple of the times were substantially more than 500 miles as well -- one 1800 mile rental, one 1200 mile rental, and one 1100 mile rental that I recall (no, those aren't the cheap single days, but still good deals, relatively speaking).

If I had taken my own car during those trips, I would have already advanced to my next oil change, the timing belt service and closer to needing to replace my tires.

I have sort of an internal rule -- I look at the miles being driven. If the cost to rent a car is $0.10-$0.15 a mile, it's a no-brainer to me to rent the car (all things being equal).

Example -- 500 mile one-day trip, cost $50-75, it pays (or at least is relatively neutral) to rent the car.

It also helps that the Hertz rental is adjacent to the on-ramp of I-459, which is what I take for most of the trips. So coming in at 1:15 a.m., I parked my car in their parking lot, and turn it in there, let them email me the receipt the next day, and take my car home.