My current car revs at 4k at 80mph. I also had two civics before... a 1984 and a 2004. both were manual and had very similar gear ratios. I know 90's miatas were geared even shorter with 4-5k hwy cruising rpm. My current car makes peak torque of 110 ish at 4200 rpm... I understand that lugging is bad for an engine... but really, is cruising at 4000 rpm any better? I understand that load vs rpm issue has been discussed before. But what I would like to know is why manufacturers undergear vehicles to such degree? At what point does higher rpm with lower load cause more wear than mid/low rpm with higher load, or vice versa?