Cruising at 400RPM you will not engage the VTEC lobes. I have well over 100K miles, have done several long cruises at 90 mph+. My car is still running great. That 20% thing is a load of crap, if that were true, I'd go from 30mpg cruising at 60, to 24mpg at 70, which does not happen. Stop and go makes you suck gas more than high speed cruising.