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The most comprehensive and easy to access resource is called the fuel economy guide.  It's published annually by Clean Cities, an entity withing the US Department of Energy.  Each guide lists every vehicle sold in the United States for a given model year, along with details about the engine type, transmission type, and fuel economy.  The list is arranged by vehicle size (midsize car, full size truck, etc.), and also by powertrain (diesel, hybrid, electric vehicle, etc.).  You can find fuel economy guides for each model year, as early as 1984.  The most recent is the fuel economy guide for 2010.

I think it's worth taking a few minutes to describe what fuel economy actually means.  From my experience, most people are familiar with the mile per gallon (mpg) terminology, which describes how many miles a vehicle can be drive on one gallon of gasoline.  So how are a vehicle's mpg numbers determined?

The federal government has described drive cycles for city-type driving as well as highway driving.  This is why people refer to mpg values for city and/or highway - they are quite different.  (For vehicles with conventional powertrains, in city mpg's are lower than highway mpgs.  But for vehicles with batteries, such as hybrids, the opposite trend is true... since a battery enables one to recover energy lost by braking (called regenerative braking), hybrids have an advantage from a fuel economy perspective compared to non-hybrid vehicles in the city, and the mpg for a hybrid is lower on the highway than in the city.) 

So what is a drive cycle?  First, the purpose of a drive cylce is to enable consumers to compare vehicles on an apple to apple basis.  Every modern vehicle sold in the US is mandated to "certify" according to the city and highway drive cycles, and hence the mpg's reported allow consumers to compare the numbers from one vehicle to another, knowing that they are truly comparable.  The city drive cycle is shown in the plot below, and is referred to as the FTP city cycle (FTP = federal test procedure).

The highway drive cycle is shown in the figure below. 

Why are drive cycles important?  Well, depending on how you drive your car or truck, you will burn more or less fuel.  One example is how you drive in stop and go traffic - if you are hard on the pedal when accelerating and hard on the brakes at each stop, you will burn more fuel than if you drive according to the FTP city drive cycle.  This is because you are "loading" the engine more... the more that you step on the pedal, the more air that enters the engine (the combustion chamber), and because the proportion of air and fuel is basically consistent at all engine operating points (it's always approximately at stoichiometric air/fuel proportions).  Another example is driving up long hills - if you live in a place like Pittsburgh, for example, you drive up a lot of hills.  It takes more energy to propel the vehicle up a hill, even if you are traveling at a moderate speed (40-55 MPH), than if driving on a flat surface, and hence you consume more fuel (fuel provides the energy, of course, for a conventional vehicle, meaning a vehicle without a hybrid battery). 

Do you have other resources that you use for learning about fuel economy?  If so, please share them!  Do you have questions about fuel economy, drive cycles, or anything else discussed in this blog?  Please let me know!!!

How do you know the pressure in your tires, or where to determine what the pressure SHOULD be?  First thing's first - find a tire pressure gauge!  It's good to keep one handy in your car, but you can also find them at the air-fill center at most fueling stations.  If you have your own compressor, you'll definitely want your very own gauge!  You can get simple, inexpensive mechanical ones, or fancy digital gadgets.  Either kind will do!

So how much air pressure is appropriate for your tires anyway?  You can check 1 of 4 places to find that answer:

• The label inside the door jamb (driver side) of modern vehicles
• Vehicle owner's manual
• Raised lettering/numbers on the tire itself
• The interweb, of course - though I recommend the other three unless the manufacturer's website contains such information, but even in that case many vehicles have multiple options so you'll have to be dilligent about acknowledging the accessory packages on your vehicle.

Once you're in the know you can top off the air in your tires!  Be careful not to overfill, of course.  If the hose you use for filling has an integrated pressure gauge then you should be fine.  Otherwise, take the time to pause, employ the gauge, and fill more if necessary!  **Tip: I recommend removing all valve stem covers and placing them in your pocket before starting - it's easy to lose those little buggers!

A few other things to check if you're using more fuel than seems normal (many of these should be updated on a regular maintenance schedule, and for good reason!):

• Engine intake air filter (you can change this yourself - refer to the user's manual and buy one at the local auto parts store!!)
• Oil change (are you up to date??)
• Spark plugs/wires
• Fuel filter (especially for older vehicles)
• Try a bottle of fuel injection cleaner, assuming that your vehicle has fuel injectors instead of a carburetor (vehicles of vintage mid-70's on should have fuel injectors)
• Top off all vehicle fluids, as necessary
• Your driving style and/or commute (I'll blog more about this topic next time!)

If you're not sure how to check these or how to know if it's time to worry about them, refer to the maintenance schedule in your owner's manual - it's a pretty useful tool, that owner's manual! 

Happy driving!!!

Mel will be here to answer all of your questions. Who is Mel? Check out the video below!