That would make sense for city driving, not having it go into OD all the time and causing wear and tear, but on the highway you needed that OD. Then in 91 with the Scud body GM put labels on the cluster "Use Overdrive for High Speed Pursuit". The 1989 & 1990 model 9C1s with the 5.7L fuel injected engine were only good to 115MPH due to drag, (190HP) But the Scud bodies from 1991-1993 with the same 5.7L 190HP were a bit more aerodynamic and could hit 130ish on a flat stretch.