On
fuelly the Grand Marquis typically gets about 20 mpg on average.
34 mpg would be hard to beat. If you're not satisfied then maybe this isn't the right car. But a small car or a hybrid could almost double it if driven with some TLC.
The things you list in your first post have been proven to have little effect, if any. Just check them out with the search button.
As you get 34 mpg you'd know a thing or two about driving economically, but at the risk of elaborating the obvious:
- Get a OBD2 FE monitor like ScanGauge or UltraGauge,
- Keep a fuel log, and log anything in it that deviates from the usual,
- Digest the 100+ Hypermiling Tips and 68+ Efficiency Mods linked on top of this page,
- Pump them tires...
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gigameter or 0.13 Megamile.
For confirmation go to people just like you.
For education go to people unlike yourself.