But all these fuel-saving options fall under a single problem: They involve purchasing a new car.

For those folks who can't afford to trade in their gas engines for something more efficient, there are simple ways to increase those MPGs that everyone desires.

Changing your worn spark plugs, replacing clogged air filters and using a fuel additive can all lead to a boost in fuel efficiency.

1. Spark Plugs

Under your hood, the performance of a spark plug is directly related to how much fuel is being consumed. Research shows that old, worn and dirty spark plugs are prone to misfires, reducing fuel efficiency as much as 30 percent.

When changing spark plugs, consider upgrading to ones that provide a faster, more efficient burn. The Autolite XP Xtreme Performance® spark plugs, which feature an iridium-enhanced, .6mm finewire design, ignite more gas and air mixture inside the cylinders, resulting in improved throttle response and acceleration.

2. Air Filters

Another way to improve the fuel economy in your existing vehicle is by changing a clogged air filter. The U.S. Department of Energy claims that replacing a clogged air filter can improve your car's gas mileage by as much as 10 percent.

FRAM® air filters are an effective solution for the everyday driver. Most FRAM air filters feature bright white fibers that make it easy to spot when a replacement may be necessary. Research from the brand suggests that motorists who change their air filter when clogged save about $173 in gas annually.

3. Fuel Additives

When your vehicle has intake valve and fuel injector deposits, it oftentimes requires more fuel to run.

Using a fuel additive like Prestone® Complete Fuel System Cleaner every 4,000 miles helps improve acceleration and fuel economy by unclogging fuel injectors and cleaning intake valves and combustion chambers. Clean fuel injectors help ensure more complete combustion and maximum fuel benefit.

Maintaining your vehicle with good-quality spark plugs and air filters, in addition to utilizing a fuel additive, will increase the fuel economy in your existing car. The end result is more money in your pocket.

With gas prices threatening to break the $4 threshold, you'll have no choice but to pay more at the pump. How often you need to drive to the gas station is up to you.