Since the autumn of 2014, drivers in the United States have been enjoying lower prices at the pump. With gasoline making less of an impact on your budget, you may be more open to getting a vehicle which gets fewer miles to the gallon. Before making your decision, you should know how much a change in the price of gas will affect your finances.

According to AAA, the national average for a gallon of regular unleaded gasoline was $2.04 at the end of November. It was 74 cents below the average from the same time in 2014, and the cost to fill up for Thanksgiving travelers was its lowest since 2008. The U.S. Energy Information Administration predicts that the average price will increase to $2.51 a gallon during the summer, but remain well below $3 a gallon in 2016.

While drivers with hybrids or compact cars are unlikely to trade them in for gas guzzlers in response to lower prices, they may give more consideration to less efficient vehicles for their next purchase. Researchers at the University of Michigan Transportation Research Institute, noting that the average fuel economy in new vehicle sales stalled last year after a steady increase, credited the trend to increased truck and SUV sales in response to lower gas prices. John O'Dell, senior editor of the automotive site Edmunds.com, says the market share of light trucks rose from 51.6 percent in August 2014 to 54.3 percent in November 2014 as gas prices declined.

Other research suggests that the cost of fuel has a limited effect on a buyer's decision. Charles Fleming, writing for the Los Angeles Times, says an increase in truck sales began before the prolonged slide in gas prices last year. However, buyers of used cars are more likely to favor efficient cars when gas prices are high and trucks when prices are low.

A study by the nonprofit think tank The Fuels Institute found that the market share of crossover utility vehicles increased from 25 percent in 2013 to 27 percent in 2014. The market share of small vehicles fell from 23 percent to 18 percent in the same period.

The organization concluded that while fuel prices will influence a buyer's decision on the vehicle they purchase, it does not have as profound an effect as might be expected. The Fuels Institute suggests that buyers are primarily interested in finding an automobile whose utility meets their needs, then try to balance it with the best fuel efficiency available for that kind of vehicle.

The decision on whether or not to buy a larger or less efficient vehicle due to more affordable gasoline should be based on your own personal budget. O'Dell suggests that such a purchase might be prudent if you need a vehicle with more passenger capacity and storage space, since gas prices currently make it less expensive to drive.

However, you'll also have to be prepared for unexpected changes to gasoline costs. Prices can be volatile, particularly when affected by factors such as refinery problems or hurricanes disrupting oil production on the Gulf Coast. If you purchase a vehicle now, you shouldn't forget about the seasonal jump in prices which arrives for the busy travel season in summer.

You can calculate how much you should expect to spend on fuel in a month by using the distance you typically travel, the vehicle's fuel economy rating, and the current price in fuel. Compare the costs to a more efficient vehicle that might fit your needs, and figure out what the price difference will be if the price of gas goes up by a dollar or two. If the less efficient vehicle will put more of a strain on your budget, you should think twice about purchasing it.

Buyer's remorse from an increase in gas prices can also work against you if you try to trade in the vehicle. When prices are high, less efficient vehicles will be more difficult to sell and dealerships will likely offer less money for the trade-in.

Consider the initial purchase price as well. Educators Credit Union, a Wisconsin-based financial institution, says larger vehicles tend to cost more than midsize and small vehicles. In addition to paying more for gasoline, you'll have to be prepared for more financing and interest costs.

O'Dell says gas prices should play a larger role in your decision if you expect to keep the vehicle for several years, since there is a greater chance that prices will increase in that period. One way to get an idea of what prices you should prepare for is to look at the average price for gasoline for the past three years.

If your budget is able to absorb fluctuations in the price of gas in the future, efficiency can play a smaller role in your purchase decision. With automakers looking to meet higher fuel economy standards, you may even find that the mileage of a truck or SUV you are eyeing is higher than expected.

For buyers who opt for a more efficient model, purchasing a vehicle while gas prices are low can get you a good deal. Demand for hybrids and other efficient vehicles is more likely to shrink during this time, making it more likely that you can purchase such a vehicle at a hefty discount.