:facepalm: I wouldn't think of ever doing that,
First you'd be way undersized - by 1.5 inches which puts your speedo out by 5.6%, so you will experience the speedo showing you a speed of over 63 mph when your actual road speed is 60 mph. Good if you have an issue with speeding
MPG? Well yes of course, it will get worse, distanced travelled at a fixed rpm, will be less with a smaller wheel while consuming the same amount of fuel.
I'd recommend a 255/50R18 - that'll drop your sidewall height by a smidge but also will be compensated by the extra width - so it will look 'shorter' as you put it.
My next 19" tires are going to be 255 series. [/color]