I hear what you're saying about the weight. I've read people are getting 50-60mpg with these engines in lighter cars. I know too small of an engine will make it work too hard so I wonder whether the Y5 or Z1 engine would be better. I was going to get an LS integra and take the back seats out and get some lightweight wheels and hope for the best. I was hoping for somewhere between 38-50mpg. Anything will be better than the 17mpg my truck gets.