Why does your wife want to keep the 3 row SUV?
We had one at one point because our kids were impossible and if they could physically touch each other, there were constant battles. We had a Yukon XL for a while (I used it to snowplow, pull a boat and pull a racecar trailer back then) and it was great because one could be in the 3rd row passenger side seat and other in the 2nd row driver side seat. They couldn't touch each other. Great for vacations. Gas is so cheap these days that who cares if it gets 15 mpg?
Typical reasons. It's bigger, feels safer, can easily fit things, it's newer/nice, etc. She also made a comment that she doesn't want people to think we aren't doing well if we sell her vehicle and get a cheaper vehicle. She knows that's not a good way to look at it but she voiced her concern. Even though she knows with almost near certainty I earn more money than all of my friends while we also spend considerably less. I told her we would get the last laugh with early retirement. I've been harping on a lot of things lately so I'm letting the SUV conversation simmer and see if she brings it up again on her own. Without prompting she has started to drive my car exclusively when she does errands without the kids so she's making conscious choices for change!
Now that you have the SUV, if you don't drive it a lot, the largest expense is the depreciation on it, not the mileage by a long shot.
If you drive 10,000 miles, an extra 15 MPG would only save you 275 gallons of fuel per year... maybe $65 per month.
You may need to trade down to a much smaller car to get 32 MPG on an older model, without paying more.
The real advantage is if you buy a cheaper car and can pocket $10,000 right now.... if you need the money, that is.