Not only mileage, a big cost increase. I bought some 13" tires maybe two years ago for around $50 each before the massive pile extra added on, the install, balancing, enviro fees and taxes. Good luck in finding 18" tires here for much under $200 here before all the fees. The stock 19" on the Challenger a bit more. If I buy another GT before they are gone, now standard 20" tires. I purposely went to a 18" for Winter rims, 235/60R18 vs 235/55R19. I remember when 60 series tires looked fat and thin sidewalls. Now those are almost like truck tires in comparison to everything 55 ratio or less due to the massive rims.H
Heck, look what a tuned up chevy II with the 194 inline was getting for mpgs... that was upper 20s low 30s right there.
One of my fieros, an 87 with the DIS ignition in an iron Duke was in the 40s mpg.
Fuel mileage was always there. Just not the butt dyno. You know what REALLY hurts fuel mileage?
The BIGGER wheels and tires that have taken over. Also a common thread between the tincan tercel was its 13 or 14" wheels, not the 18. 19. 20 or bigger that even cars get these days.