The biggest issue affecting gas (not diesel) mileage isn't "government insanity" (is that a technical engineering term?). Most of the EPA mandates don't actually hurt mileage, but they do cost money. Some actually help mileage (o2 sensors optimize fuel/air ratio, etc.).
The biggest thing to affect gas mileage is weight, plain and simple. A lot of that is because of safety features, doors that don't fold on you, air bags, etc. all of which you may not appreciate until about .5 seconds before you wreck your car. The other big factor is "luxury" features. When was the last time you saw a car that didn't have power windows? Power locks? AC!? Can you even buy one like that in america?
A 1987 civic wagon weighed 1900lbs, a 2014 civic sedan weighs 3000. Some of that is safety, and a lot of it is luxury features people "have" to have.
It's a combination of the EPA reducing efficiency of engines and the DOT increasing the weight of cars... A two pronged approach of reducing MPG, forcing people to buy overpriced vehicles they would not purchase if lighter more efficient vehicles were legal to produce.
EPA limits on gasses such as NOx, produced in greater quantities with higher pressure and temperature in teh comustion chamber. An optimal ignition timing curve results in NOx levels bureaucrats outlaw, along with greater power output and more MPG. Result is a less than optimal timing curve and reduced MPG.
EPA CAFE requirements made it illegal for people with families to buy fuel efficient (20-25 MPG at the time) station wagons and replaced them with SUVs getting 10-15 MPG.
The DOT required safety mandates add tremendous amounts of weight to cars, reducing MPG and ironically safety as well. Bumpers, roofs, A/B/C pillars, etc. Drive an 80s or earlier vehicle then drive a vehicle made in the past 10 years. You'll notice you have very little visibility in any direction. Very wide pillars, front and rear head restraints, very tall (and now heavy) doors all infringing upon visibility through the tiny windows and tiny mirrors that magnify a tiny tunnel of space behind the car. So then teh DOT mandates even more weight and complex distracting (not to mention expensive) systems such as radar proximity indicators, cameras, fancy displays. It all adds up, to reduced chances of avoiding an accident altogether, decreased MPG, and of course increased cost.
Cars 50 years ago were getting mid 30s MPG without fuel injection with real time feedback and mixture adjustment from O2 sensors or overdrive transmissions. Imagine the fuel economy that is possible (and the low cost it can be done at) without the threat of government violence. Even 25 years ago you could buy a brand new cheap car that got 50+ MPG and that was still hindered by EPA and DOT mandates, whihc I suspect drop 10-20 MPG from what could be done.
http://blog.motorists.org/50-mpg-then-and-now-2/And if you want to drive those cars, you still can and get the gas mileage to go along with it, but my guess is you drive something a lot newer. Which has power windows :-)
Yes, I still can drive those cars. You're guess is wrong because I still do drive those cars. Part of my criteria for cars I'll drive are no power accessories, no government mandated wide pillars restricting my field of view, no tiny government mandated mirrors restricting my view to the rear. I've also been in a few wrecks (all caused by other drivers) in vehicles over 30 years old, there's nothing to be afraid of. The government has also done tremendous harm to the poor and (truly) middle class with their cash for clunkers program which destroyed many perfectly good, cost effective, and reliable vehicles while tripling the price of cheap used cars by creating a sudden artificial scarcity.