Hard to believe a 91 Monero with 33s and automatic could get 21-23 mpg in 50:50 city/highway mileage. I would expect 15-16 to be normal for this vehicle. Maybe you used to drive downhill both ways before <img src="/forums/images/graemlins/smile.gif" alt="" />.

1991 Montero LS, fading red paint
Front and rear limited slip differentials
95 SR Rear Springs, torsion bar crank, 137,650 miles
33x12.5 ProComp Mud Terrains, Bushwacker Fender flares
3 litre V6 with new heads