All true and age does make a difference to design, however i had a Mercedes 190D 2.5 from 1991 and the insulation was amazing inside. You could not hear the engine running although with the bonnet open it sounded like a diesel tractor, from the inside totally quiet. So i think rather than age, it is what the factory engineers put into it to reduce noises. For example, the Mercedes 190 had like asphalt mats on the underfloor to dampen noise from road, tires.....etc...and it worked. I never rode an RX, so i cannot compare yet.