I did some back-of-envelope math and I think MMM would actually be better off selling his 40 MPG xA and using his 27 MPG Odyssey for all his driving.

Assumptions:

-xA is worth $5k if he were to sell it

-xA gets 40 MPG

-Odyssey gets 20 MPG

-Gas is $4/gal

-Insurance on the xA is $20/month (not sure of actual figure)

-MMM drives 5k mi/yr

Driving the Odyssey 5k miles at 20 MPG burns 250 gallons of gas, or $1000 worth at $4/gal.

Driving the xA 5k miles at 40 MPG burns 125 gallons or $500 at $4/gal.

So, $500 extra to drive the Odyssey over the xA. But, assuming he spends $240 insuring the xA, that figure decreases to $260.

$5000/260 = 19.23 YEARS he would need to drive the xA to make up that difference. And this figure doesn't even account for tires, oil, and maintenance on the xA, nor the investment gains he would make putting that money to work. Plus the Odyssey gets more than 20 MPG, the xA is likely worth more than $5k, and gas will likely remain below $4/gal for the foreseeable future, so it might be more like 25 years before he breaks even.

Keeping the xA around sure seems like a losing proposition to me. What do you think? Am I missing anything?