
Most of us, are at some point, going to own a car. Odds are that in the US that will be the gasoline-powered vehicle (although diesel, hybrid, natural gas, and electric vehicles are now available and increasing in numbers). The basics of the vehicle are that liquid fuel has the stored chemical energy that is released during the combustion process to power the car. It is an old technology. The Model T Ford ("available in any color as long as it was black"- Henry Ford) in the US was available in 1908. Diesel engines predate gasoline engines. Interestingly the Model T Ford managed 12 mpg - some of the passenger vehicles (SUV's for example) on the road 100 years later, achieve only a marginal increase at 18 mpg. This is one of the major issues with energy use - efficiency, measured here by miles-per-gallon (mpg). The lower the mpg the more gasoline is needed to cover the ~14,000 miles the average American drives annually, and thus more air pollution. This used to be a major source of the balance of trade challenge but now the U.S. is producing much more domestic oil and natural gas so imports are declining.

Vehicle Ownership is Higher in the United States

So almost 8 out of every 10 people in the US own a vehicle. This is much higher ratio than the rest of the world where much lower ratios are common. Car ownership, however, is increasing dramatically as the industrialization of the developing world continues. Recall too, that the population of nearly all of these countries is increasing, so the potential for more people to be driving more miles in a greater number of vehicles will, of course, create more pollution - at least given the current technology. China is one such example: lots of new vehicles but lots of pollution! Current technology, as we will see later in this lesson and others, is evolving. Our air is getting cleaner in the US (EPA air quality).

Aerodynamics & Efficiency
Think about riding a bike, or roller blades - when you crouch low to reduce your drag (making you more streamlined), you reduce your wind resistance, allowing you to coast further before having to pedal or push off. In modern cars, having your foot on the accelerator doesn't mean you're actually accelerating - you could just be maintaining your speed, and working against the energy losses of friction and drag, which requires more energy (gas) just to maintain the same speed. Having a streamlined car helps to increase the mpg this way, or, in the case of sports cars, achieve a faster velocity.

Mass Issues
We have discussed kinetic energy. Recall Ke=1/2mv2, thus, the heavier the vehicle (greater mass) the more energy is required to move the vehicle. Saving weight in vehicles is one way to increase the mpg, by taking out the full sized spare and replacing it with the "doughnut" tire saves weight and increases the mpg. Changing body materials to lighter plastics, metals, or fiberglass is another method. Making engines lighter by replacing the steel motor with ceramic components are also being considered. Please watch the following (:33) video. Vehicle mass is even more important with electric vehicles as they currently have driving ranges that are lower than desirable. The Tesla for example does not carry a spare tire (it comes with a tire change service).
Click for a transcript.
[Video opens with Dr. Mathews standing in front of a corvette stingray.] Dr. Mathews: You might recall that force equals mass times acceleration. So if you have a certain amount of force made by a certain engine, you want to have a faster acceleration. One thing you could do is reduce the mass. This is what happened in the Corvette. It is actually made out of fiberglass so it could accelerate faster. If you lower the mass of the vehicle it will also increase the miles per gallon. Not the case here though, we are after speed. [Dr. Mathews gets in the Corvette.] [Video ends]
Efficiency Issues

Heat losses from the engine, air resistance, and rolling resistance between the tires and the road all contribute to our vehicles achieving only about a 28% efficiency. This means that only 28% of the total chemical energy supplied in the form of gasoline is actually being utilized, leaving 72% of gasoline's potential energy content to go essentially unused. This is one of many areas in the automobile industry where future improvements are expected.
With climate change concerns, there will be significant pressure for more stringent standards for automobiles (President Obama's statements). We have made some significant improvements in this area after decades of inactivity. However, the Trump administration has slowed the rate of this and other transitions — are potentially rolling back the efficiency standards (standards are under review).

Appropriate tire pressures are usually written on a sticker on the inside of the passenger compartment. Remember that the rolling losses heat the tire up and the gas inside, so don't measure tire pressure on a hot day after a long drive. Also check tire pressures again when the seasons change, for example in the winter you may need to add more air to pressurize to the appropriate level.
How you drive also influences your mpg. Check out the fuel economy website and this MotoWeek movie clip.
You can always watch Mythbusters and argue about windows up/down/ac influences or tailgate up/down for you truck owners.
The End of Gasoline?
In 2017 there were the first indications that gasoline vehicles may be replaced by hybrid, electric, or renewable fuels. France is proposing a ban on diesel and petrol sales by 2040, and Volvo is dropping gasoline-only engines (will still allow hybrids) in 2019. So, pressure on gasoline is mounting but it has many advantages: dense energy (high calorific value), availability, and can be efficient with the correct vehicle. I expect we will still be using it the decades to come but expect climate change concerns to increase the pressure.