Trying to improve your gas mileage? Use biodiesel? Or just want to save a buck?
With all the hoopla around different fuel and vehicle choices these days, it’s easy to be confused. Hybrids? Diesels? Biofuels?
Which one of these choices is actually best for you?

While there isn’t necessarily a clear winner in terms of environmental friendliness, each option has some particular pros and cons that I’ve compiled here. I’ve tried to stick to options that are readily available, so things like fuel-cells and electric cars will have to wait. Want to kick the oil habit? Here are some options:

1. & 2. Get rid of your car / Walk or Drive Less.

Ok, obvious one first. For some, ditching the car isn’t an option. But
if you live in a city with decent public transportation, or a smaller
town (< 50,000) this may be your best bet. Consider walking, biking,
carpools, or public transport. Also consider moving to a walkable area. As Sheryl Canter from ED so aptly put it: "If you live in a car-dependent area, moving to a walkable area will do
more to fight global warming than buying a fuel-efficient hybrid car."

PROS:

• health and well-being decreased stress

• decreased pollution and Greenhouse Gas (GHG) Emissions

• increased savings (vehicles cost, maintenance, fuel, insurance)

• participation encourages pedestrian-friendly city planning

CONS:

• public transportation unavailable/unreliable in some areas
• can be difficult to walk or bike especially in certain seasons (or can be impossible due to distance > 5 miles)

CONCLUSION: When feasible, the single best thing you can do for your wallet, the environment, and your community. For some ideas and a real-world example, check out Kelli’s post: Why I Sold My Car, or How I Learned to Stop Driving and Love the Bus.

3. Hybrids/Plug-in Hybrids.

Popular and a good bet for many, especially for city driving.

PROS:

• significant increases in mpg (~46 mpg)
• significant state and federal tax credits
• save on fuel costs
• 2008 models may blow the competition away by doubling fuel efficiency (94 mpg)

CONS:

• still uses gasoline
• mileage not always as good as comparable diesels, which are considerably cheaper
• not useful for all climates/locations/users
• these vehicles are usually expensive

CONCLUSION: Hybrids have always seemed like a lot of technology for little gain, considering that a 1982 Datsun Diesel gets the same mileage as a 2008 Ford Escape Hybrid - but they still offset gas guzzling vehicles that might otherwise be on the road. While often expensive (around $22,000), tax credits can soften the blow by several thousand dollars and may even make the cost comparable to other new vehicles. You may also be able to find cheaper new or used gas models, like the Toyota Corolla, that get good mileage (37 mpg highway). But the 2007 Toyota Prius tops the charts at 45-48 mpg. And we can expect newer models to get even better.
Also see Joshua’s new post: Prius No Longer Golden Child of Green Motorists.

4. Buy a diesel and use biodiesel.

May be the most environmentally friendly option.

PROS:

• decreases most pollutants by 50% (when compared to diesel fuel)
• decreases net greenhouse gas (GHG) emissions
• no engine conversion needed
• fuel not as harmful to humans/environment if spilled
• fuel can be produced locally
• more vehicle choices than hybrids
• can get better mileage than hybrids while using renewable fuel
• older diesel vehicles can be cheap
• new 2008 diesels will be cleaner (emissions-wise) than comparable gas engines

CONS:

• biodiesel not always available or convenient
• have to blend it with diesel in winter (usually at 50%)
• feedstocks may be questionable - food competition concerns
• older diesels produce 10-100x dirtier emissions than comparable gas models

CONCLUSION: Buying used newer model diesel vehicles is a popular choice where biodiesel is available. Some models, like the VW Golf, Jetta, and Passat, can get upwards of 45-50 mpg on regular diesel or biodiesel. While older diesels are dirtier at the tailpipe, using biodiesel can offset considerable carbon dioxide emissions. To find an old diesel, try Craigslist or Autotrader.
To find a local biodiesel pump, try this map.
If you need to find biodiesel on the road, there’s now a biodiesel tucker hotline, 1-866-BIODIESEL (246-3437) that will help you locate the nearest source of fuel.
List of new diesel vehicles available.
More on biodiesel: Biodiesel Mythbuster.

5. Buy a diesel and convert it to run on straight-vegetable-oil (SVO).

For people that want to kick the oil habit, but still need a vehicle.

PROS:

• only fuel that can be carbon negative
• fuels is a recycled waste product
• waste oil is usually free
• never stop at a gas station again (almost)

CONS:

• requires considerable investment in vehicle conversion and maintenance.
• requires getting your hands dirty (or rather, oily)
• waste oil requires time/effort to process. may be difficult during certain times of the year (cold winters) or without proper facilities.
• may eventually be limited by consumer demand
• regulatory structure not in place for SVO. requires personal responsibility to pay road taxes
• lack of refining may increase harmful pollutants (such as acrolein) from combustion
• no available long-term studies support or refute the use of vegetable oil in diesel engines

CONCLUSION: SVO works great for all kinds of people, but requires significant commitment in fuel acquisition and use. Using waste vegetable oil can almost eliminate fuel costs, although legal use still requires paying a nominal sum in road taxes. This is generally not a choice for the faint of heart, but is gaining popularity.

For more information, try the VegTruck blog.

So which one is best?
Hybrids and newer diesels running on biodiesel tend to be the most popular options, and for good reason: great mileage, comfort, availability, etc. For now, a hybrid may be your best bet if you can afford it (and if that type of car works for you). Those of us with smaller bankrolls can still get by on high-mileage gas models or diesels. In terms of environmental benefits, buying a used, high-mileage diesel (like a VW Jetta, Passat, or Bug) and running the highest blend of biodiesel available, may have the most significant environmental impact. There are plenty of used diesels out there in good shape, and for more adventurous types, many waiting to be fixed up. Keep in mind that buying a new vehicle entails considerable embodied energy costs that may not be reflected in the sticker price. Looking to the future: in 2008, expect drastic changes in both hybrids and diesel models, including dramatic increases in fuel economy and cleaner emissions.

Good Luck!

Kiplinger: Best Values in Clean Cars
eMagazine: Here Come the Cleaner, Greener Cars