... I think the universal adoption of closed loop fuel injection was driven mostly by emission requirements, but it also keeps engines from running too rich and getting oil dilution that accelerates engine wear. ...
Yes. It also prevents the engine from ever running lean and burning out the exhaust valves or spark-plug electrodes, and makes them much easier to service--just plug in a code reader and ask it what's wrong.
Removing lead and sulfur from gasoline was also mandated by air-quality regulations. That, too, contributes to a cleaner engine that is less prone to misfires (which reduce power output and increase fuel consumption) due to fouled spark-plugs, or preignition due to deposits and hotspots.
... I think modern synthetic oils with improved additive packages would've prolonged the life of even the older cars.
Not much. The oil-change interval in older engines is determined mostly by contamination, and consumption of the additives that neutralize contaminants, not breakdown of the base oil, and you still have the older, softer alloys if the engine hasn't been rebuilt recently. Modern engines also have better dimensional tolerances and are stiffer, especially those with a structural oil pan. When the block flexes, clearances change and sometimes there's metal-to-metal contact.
... I believe that some of the reduction in the strength and stiffness of structures in today's cars compared to those of many years ago is so they can give way and crush in specific areas to absorb energy in [a crash]. Also weight reduction for fuel economy is another factor driving that trend. ...
Unibody construction is inherently stiffer than a frame that's only a few inches tall, especially against torque in the roll axis. (in body-on-frame design, the body contributes little or nothing to strength or stiffness; it's just along for the ride) And yes, there is a passenger compartment designed to remain intact and crumple zones designed to absorb energy. (look closely, and you'll see a few holes or notches put there to predictably initiate bending) When contemplating the results of a crash, look at the body as a composite of different components, not just "the body" as if it were one monolithic design.
This film clip dramatically illustrates the difference. "Cars survived a crash much better back in the day"? Hardly.
in all fairness, cars designed after the 1966 Federal Motor-Vehicle Safety Standards took effect would have done much better. The per-mile fatality rate dropped by half between 1966 and 1976, as pre-FMVSS cars aged out of the fleet)
This one's even more dramatic. The driver of an old banger fares much worse than the driver of a modern car designed to the
Euro NCAP standard, despite being surrounded by a half a ton more steel.
Never underestimate your engineers, if given proper direction (or government regulation) and a free hand.
