Some say buy a 2nd commuter car, but the math doesn't work.
Say you buy a beater Camry that gets 35 mpg. By the time you buy the car, pay the tax/ tag/ registration fees, and insure it, you're upside down already on any savings you'd get from the 4runner's 18.5 or so average mpg to the Camry's 35 mpg. Add in maintenance and you're really sunk.

Now if your fun vehicle is a fully built mostly off road rig, an around town and road trip car like a Camry would be nice to have as a 2nd vehicle.

PS I drive like I'm on a leisurely Sunday cruise 90% of the time and still only manage about 18 city and can get 22 or so highway but that's more in the 65-72 mph range. Over 72 the mpg drops quickly.