Weight. It's all about trying to get those mpg numbers with performance all that extra weight. All the added safety equipment weighs a lot. The HF had a seatbelt and that was it. An '88 CRX HF weighed just over 1800 lbs. 1800!
For highway trips especially long ones, I'd agree weight is key, and respectfully add that, in addition to (i) weight, the key issue is DRAG force, a combo of
(ii) speed, (iii) drag coefficient, and (iv) frontal area, and then
(v) engine efficiency vs power&rpm, especially the peak, min_BSFC, and its match to he highway powerload,
and then
(vi) tire design&inflation.
DRAG: The dominant highway Drag factor, profile drag, has equation 0.5*velocity^2*air_density*drag_coeffi* A_frontal, or
Fprofile_drag= rho*v^2*Cd*A/2.
(ii)
THE SINGLE BEST THING AMERICANS CAN DO to improve mpg, lower gas costs, save lives, lower maintenance & wear, and stop funding Vladimir Putin's aggression and Saudi Arabian aggression, LIKE 9/11 and TALIBAN victory in AFGHANISTAN, AND lower global warming and particulate pollution ,
IS TO SLOW DOWN especially on the highway.
Slowing just 10%, from 75 to 67, can lower your GAS COST by about 15%. That could be say $10 per tankful that you save and don't give to Exxon, or
Putin's war machine or Saudi funding to the
Taliban.
(iii-iv)
Cd*A: It'd be hard for carmakers to lower frontal area much, for given car type&class, but the Cd can for many models be improved a LOT, especially say for the current full-size pickups that have flat overly large grilles etc. I think the CRX HF had a Cd of only ~0.25, while full size pickups seem to have varied Cd's of about 0.35-0.50..
that's 40%-100% higher, so there is lots of room for improvement, say using racing experience, like efficient frontal designs, smoothing of underbody, Kammback, etc.
[Improving CRX aero - Honda-Tech - Honda Forum Discussion]
[Pickup truck aerodynamics - Page 5 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com]
(v)
ENGINE EFFICIENCY for gas ICEs the best is usually at close to full power; so an oversized engine (eg 7-liter Semi) will almost always run part-load very inefficiently and add useless block&frame&tank&radiator weight. Hybrid power plants help even on the highway, since the electric system can keep the ICE running steady at or near its optimum, min_BSFC. So choose the smallest engine that meets your needs, with needs really set by your torque and
gradeability requirements, the latter at your max payload&trailer weight and altitude.
IMHO acceleration is insanely overrated.. I drove a 220D Benz with a 0-60 of 25+ seconds, and I was okay. You don't need 5s 0-60, or even 10s. Trucks have 0-60 times of say 20-40 s.
Buy the right-sized engine, lower the weight,
and keep your money: Detroit/Fiat-Chrysler-Ram, Putin and the Saudis already have more $$ than they need let alone deserve.
TELL YOUR DEALER YOU WANT EFFICIENT VEHICLES. plug-ins even better, power takeoff, quiet off-roading, etc.