you can haul or tow what ever you want. I used to have a 1986 Toyota, 2Wd, 4 cylinder,4 speed truck and I used to tow cars with it all the time. On the highway it was fine,on hills it sucked,but it got the job done.
I have a Nissan Frontier, 4-cyl and find that it would be nice to have a v-8, but the 4-gets the job done. The gas mileage difference is negligable. The main concern with towing is making sure you don't tow something so heavy that it compromises the stability, braking and traction of your tow vehicle.