I'd be concerned moreso with longevity and reliability when putting a 4 banger in one of these SUV's... I personally am still skeptical of them being in trucks. Sure a smaller engine gets better gas mileage, but that's when you drive it casually. Push the RPM's into a 'lively' driving range, which is incredibly easy to do in a 4cyl, so that it doesn't take forever and a day to get somewhere, and mpg's plummet.. and fast. Add considerable weight along with it, and then add a trailer on the hitch... even if a 4cyl could do it, it's going to be screaming the whole way, working much harder than any V8 would have to to accomplish the same thing. As with everything in nature, the faster the heartbeat, the shorter the lifespan. Even if you save some mpg's, gone would be the days of a 300k-400k odometer.