You can increase mileage by increasing your tire pressure. I run 55 lbs. The ride will be more harsh.
You will get various opinions on the spark plugs. They last 100,000 miles, so, IMO, the extra expense of the factory plugs is worth it.
Custom Turbocharger System
Genesis Charger and Discharger
NM license plate KERS
(Kinetic Energy Recovery System)
Scott's front and rear springs
GAZ rear shocks
2003 Lean Burn CVT (Wife's car)
2000 Citrus with aerodynamic extension
2002 Blue getting new engine