So far, I have gathered that this is what you should do to save gas, in order from the quickest, easiest, and cheapest ideas, to the more expensive, inconvenient, uncomfortable, dubious, and/or difficult ones.
1. inflate tires (to at least the maximum recommended on the tire walls)
2. throw out extra weight: clean out the beer (root beer of course, officer) cans and bottles, etc
3. change your driving habits: drive slower, accelerate more slowly, try to do acceleration on downhill slopes and avoid accelerating on uphill, coast up to stop lights, shut engine off when stopped.
4. change to lighter weight oil
5. install a gas mileage indicator (to help with #3)
6. Maintenance: Keep engine tuned. pay special attention to the O2 sensors
Those are the easiest and best. From here on it gets worse with respect to sacrifices, significant expenses, dubious benefits, or decreased safety.
7. Limit power use: no A/C, no loud radio, drive in daytime so won't have to use headlights. change incandescent bulbs to LEDs.
8. upgrade to low rolling resistance tires.
9. More radical changes in driving technique: Shut engine off while coasting (not always legal, is that?) and master technique of restarting engine with clutch rather than starter, make high G turns rather than touch those brakes,
10. more serious weight reduction: dump the spare tire and jack and carry a cell phone and an emergency number instead, trade out steel rims for lightweight aluminum, replace steel hood and fenders with carbon fiber (if available for your vehicle), maybe trade out glass side and rear windows for some sort of plastic, toss out the passenger and back seats
11. trade up to a more efficient car (if what you have is nothing special)
12. aftermarket engine upgrades: headers instead of stock exhaust manifold, camshafts specially tuned for FE . Hotter thermostat, electric fan for radiator (well, most cars do that nowadays), chips.
13. do it yourself aerodynamics: make skirts for the wheel wells, spoilers, build up back so it's more like a teardrop shape, do something about the side mirrors, and do what you can to smooth the underside.
14. add solar cells to lighten the load on the alternator.
15. Or dump the alternator and change to a deep cycle battery, and get a charger. recharge often.
And now, to boldly go where no one has gone before. Or very few have gone, because it's so uncertain and heart stoppingly expensive.
16. Radical body: Acquire a body made entirely from lightweight material, be that aluminum, magnesium, or other alloys, or composites. How one keeps it street legal, I don't know.
17. Radical engine work: make something that can burn methanol, and dispense with the radiator and water pump (Scientific American article from some 10 years ago), go with a dry sump (Hey Smokey column in Motor Trend from years ago), and where oh where is the 42V standard will all the cool gas saving features like electrically actuated valves with whatever timing was desired and no losses from camshafts, a single winding for both alternator and starter integrated with the flywheel and the wonderful ability to instantly start, etc. Still all ICE tho.
No doubt I missed plenty of ideas. And please discuss the ordering. I'd like to see something like the above list somewhere, perhaps as a FAQ. Or is there already such a list?
Actually I like them all! I think vehicle modification can be a great supplement to driving style. I wouldn't be able to get the most out of my old Integra without tweaking the vehicle to 21st-Century efficiency changes.
I personally have added:
Hotter Thermostat (170F=Stock; added 192F)
OEM Engine-Block Heater
Low-Rolling Resistance Tires
Modified Engine Air Intake for Temps (to be further tweaked)
Cruise-Control Throttle Limiting System (CCTLS)
Exhaust manifold heat shield delete
Seafoam Cleanse followed by a PCV Catch Bottle
Loosened the Auto-Trans Throttle Linkage
The above mods and driving style have helped me go from 26mpg when I first started to what you see below.
The car is always a work-in-progress but so is the driver
From my experience, so far, I'd definitely add grill blocking to your list. I'd rank it as up their around number 4, as far as benefit and the cost is pretty much nothing. I've done a crude grill block, with some noticable benefit and I'm in the process of trying a little more aerodynamic shaped grill block. When I have some results which I can somewhat quantify, I will post that information, but right now all I can report is that it does make a much more noticable improvement than I would have anticipated.
Another change, which I have not yet imlemented, although I have acquired some of the necessary parts, is to make a transmission/gear change, to allow the engine to run at a lower rpm. In examples taken from members of gassavers, this change has added considerably to the mileage capabilities of both Honda Civics and Geo Metros. I'd rank it more around 8-10, primarily because it requires time, effort and generally some portion of cash expense, to accomplish.
Don't drive when you can walk or bike is a great one. On a similar note, spend a bit of time with maps working out the most FE routes. I image they'd almost always be the shortest routes.
Picking good parking spots definitely belongs with better driving habits. When a store I want to visit is on the left side of the street, I sometimes park on the right and walk across.
I forgot "drafting". Should add "Tailgate big trucks when possible" to #9.
Grill blocking: Sounds fairly easy. I don't entirely understand it yet. This is not blocking off air to the radiator or air intake, this is only stopping air from blowing into the engine compartment from around the sides of the radiator, right? And it is very effective, is it? Anyway, grill blocking sounds a lot easier than other aerodynamic mods, so ought to put that in, let's see... between 6 and 7? Or, as suggested, even better than #4 changing to lighter oil.
Golf ball style dimples: The dimples on golf balls reduce drag. I've wondered for a long time whether that would work on cars, and envisioned having the entire surface covered with little dimples just like on golf balls. A few years ago Corbin Motors produced the "Sparrow", a 3 wheel electric car. (One was used in Austin Powers 2 or 3.) I managed to visit and take one for a short test drive, when they were still in biz. I noticed that the body panels at the rear of the Sparrow had golf ball like dimples. Those dimples were much larger, perhaps about 3 or 4 cm across, and were only at the trailing edges.
How about lobby for better roads? Some ideas: Shorter roads of course. Straighten out roads, intersections should be raised (except in icy climates maybe?), avoid excessive stoplighting and stop signs, improve timing of lights. And, FREE ALL TOLL ROADS! Tack on another few cents to the gas tax. Don't make people stop to toss a few quarters into a bin or hand bills to a toll collector, and then wait around, engine idling, while the bin figures out if you put in enough money or the operator fumbles with your change.
Fill tires with pure nitrogen or helium. I left that one out because I think it would be of nearly no help to FE. Saves, what, maybe 1 pound of weight? I read that pure nitrogen is good for other reasons-- less corrosive, so rims and tires will last a bit longer, doesn't leak out as readily, and less variation in pressure from temperature changes.