nnik

BTW...speed limits were dropped to 55mph from 70 mph in the 1970's to save fuel because of the energy crisis

945LSTANG

maybe, who knows.

either way, im sure ford would select the figure that makes their motors appear more efficient. i just don't see how modified cars are getting better fuel mileage than their stock counterparts. maybe im missing something here...

69MustangCoupe393cid

That's only partly valid IMO, that was back when we didn't have OD gears or at least most vehicles didn't (yes some newer ones had them "read: 70's", but even at that it was something like .8:1). It was also back when pretty much every car had this thign called torque. Now we have these stupid torquless engines that have to turn galactic RPM's to make any power. I mean granted you had rear ends that were just made for straight highway, but it was a different time period, because now we have the hard core car guys that have the 4.10's+ in their DD's, but only due to some nice OD gears. That was almost impossible to have back then, because you had you're high gear in the trans at 1:1 in most cases if not all, there were no .5:1 OD gears to give us the best of both worlds.

Mild mods like intake and exhaust can make it run more effieient, that I can see, hell even some nice turbo setups can get pretty good mileage. It's all about the volumetric efficiency of the engine, and lets face it, not all cars that roll off the factory are performing at their best. There are definitly certain mods that will hurt mileage, and some depending on how bad the factory was, that would help.