[MetroMPG]

(This list is a work in progress - will be adding links to related threads.)

Transmission & engine

• Installed transmission with taller final drive - 5.2% improvement
• synthetic transaxle oil - untested
• efficiency camshaft from XFi model installed March 2007 - untested
• lower viscosity synthetic engine oil (at first: 5w30 2L + 0w20 1L), changed to full 0w20, summer 2006 - untested
• timing advanced - untested
• engine block / coolant heaters (on the Blackfly) - Update: April/07 installed additional 850w inline heater
• alternator disable - ~10% improvement
• warm air intake (WAI) - tested
• K&N air filter (Busted! Removed & sold. See Testing a 'performance' air filter for MPG)

Aerodynamics

• prototype removable boat tail - ~15.1% fuel economy improvement
• partial grille block & rear wheel skirts - ~5.7% improvement
• streamlined wheel covers - untested
• deleted passenger outside mirror - ~2.3% improvement
• Kammback hatchback extension - ~4.9% improvement
• radio antenna repositioned - untested
• gap filling around headlights - untested
• hood/bumper gap sealed - untested
• partial cowl block - untested
• smooth undertray - ~2% improvement
• gap filling around headlights - untested
• massive cardboard air dam - tested

Other

• tire pressure 38 psi (front) 36 (rear); boosted to 48/46 Feb/06; again to 52/48 fall/06 - tested
• LRR tires (Bridgestone Potenza RE92 from 1st gen Insight)
• lightweight 14 inch alloy wheels (with wheel discs)
• aftermarket cruise control (only used for testing, or on flat roads)
• new brake calipers (on Firefly #1 - the original ones were dragging slightly & replacement noticeably improved rolling resistance)
• daytime running lights switch - so I can turn them off on a divided freeway, where DRL's safety contribution is lowest. (It's highest on undivided highways where there's an oncoming overtaking hazard, and where other cars are approaching your path at right angles - e.g. urban driving).
• engine kill switch (to keep the ScanGauge alive if the engine is stopped while at rest or coasting)

Tools

• a good tire pressure gauge
• a ScanGauge
• Accessing the brain trust at EcoModder.com
• Books: Road Vehicle Aerodynamic Design by RH Barnard; Aerodynamics of Road Vehicles edited by Wolf-Heinrich Hucho