Many drivers are constantly challenging themselves to find new ways to improve the fuel economy of their vehicles. According to the U.S. Energy Information Administration, in July 2020, for all grades of conventional gasoline, the average price in the U.S. was $2.272 per gallon.

How we drive has a significant effect on our mileage: driving at slower speeds, going easy on the gas and brake pedals, and properly using cruise control are all strategies for achieving better fuel efficiency. Likewise, a well-maintained vehicle with properly inflated tires and good alignment can also stretch the gas tank further.

Key Takeaways

  • Driving at slower speeds, going easy on the gas and brake pedals, and properly using cruise control are all strategies for achieving better fuel efficiency.
  • A well-maintained vehicle with properly inflated tires and good alignment can also stretch the gas tank further.
  • There are a number of additional vehicle modifications that can help individual drivers improve their fuel efficiency, including real-time engine monitoring, vacuum gauges, grounding cables, and pickup truck caps.

Combining good driving habits with careful vehicle maintenance can certainly have a positive impact on your fuel economy. However, there are a number of additional vehicle modifications that can help individual drivers improve their fuel efficiency.

Real-Time Engine Monitoring

These devices plug into the vehicle's On-Board Diagnostic System or OBD II, the updated on-board diagnostics standard in vehicles sold in the United States since the beginning of 1996. These devices provide streaming data, including battery voltage, coolant temperature, and a real-time fuel economy readout. Fuel economy instrumentation, such as ScanGauge's OBD II Computer or the CAMP2 from HKS, measure fuel quantity data from the vehicle's injection timing. In short, the longer the injectors remain open, the more fuel is released.
How do these devices improve fuel efficiency? Drivers get instant feedback on how their specific driving habits affect mileage. If you gun it off the line, the display will likely reveal an immediate (and significant) drop in fuel economy. Drivers learn to accelerate smoother and drive a bit slower.

Vacuum Gauges

A vacuum gauge is a low-cost, low-tech device that provides instantaneous fuel economy measurements by monitoring the manifold vacuum. It works like this: A higher manifold vacuum equates to higher mileage. Similar in appearance to other dashboard instrumentation, these dials let users know how well they are driving in terms of fuel efficiency. Through practice–and with the vacuum gauge's feedback–drivers can learn to accelerate in ways that maintain high and steady gauge pressure.

Grounding Cables

Grounding wires and cables are an integral part of a vehicle's electrical system. A vehicle depends on an electrical network–fuses, relays, and electrical wiring–to operate systems such as lights, fans, stereos, and air conditioners. All of these systems share a common ground because they are all connected to the battery's negative terminal. As the connections wear out or loosen, resistance increases (because the amount of conductive material decreases). As a result, everything in the electrical system has to work harder. This can lead to a variety of problems, including slower throttle response and decreased fuel efficiency. Quality grounding cables can improve your car's performance and gas mileage for a relatively small investment.

Pickup Truck Caps

The open bed of a pickup truck is a trap for wind. This can reduce the truck's aerodynamics and can cause substantial drag. Both of these factors can reduce fuel efficiency. Truck caps and tonneau covers can both improve aerodynamics. (Tonneau covers are low-profile bed covers that allow air to flow smoothly across the back of the truck.)

Some companies will build custom aerodynamic truck caps that reportedly improve gas mileage by 13% to 20%. Slanted from the top of the truck's cab to the top of the tailgate, they greatly reduce drag by increasing aerodynamics.

Weight Reduction

Every additional 100 pounds in a vehicle equates to a 1% to 2% increase in fuel consumption. And the smaller a vehicle is, the more it is impacted by any excess weight. Drivers should leave behind the golf clubs, the box of tools, and any other unnecessary items that end up stored somewhere in their vehicle.

While modifications can save you money and fuel, which is good for you, your car, and the environment, caution should be exercised to avoid any modification that could affect the safety of the car.

Another approach is to actually remove or substitute parts of the vehicle. For example, taking off unused roof racks (which can reduce weight and drag), removing unused seats, replacing rims with lightweight alternatives, or replacing the spare tire with a can of tire sealant. In addition, filling the gas tank only partially, instead of all the way, reduces the overall weight of the vehicle. Fuel weighs about eight pounds per gallon; depending on the fuel tank capacity, that could mean driving around with 50 to 100 fewer pounds in the car.

Fluid Modifications

Using the lowest viscosity engine, transmission, and differential oils recommended by the manufacturer can improve gas mileage. Thinner oil reduces resistance. In addition, synthetic oils have more stable viscosities as temperatures change; this can further decrease resistance. Synthetic oils are more expensive but they tend to last longer because they don't break down as quickly as conventional oils.

The Bottom Line

In the past, some care owners (particularly those that owned so-called "muscle cars") spent a significant amount of time and money trying to increase the speed performance of their cars. Times have changed. Now, many car enthusiasts are more concerned with maximizing fuel efficiency. And simple car modifications, such as ditching the roof racks and adding a vacuum gauge, can improve fuel efficiency.

Other projects, such as altering the vehicle's shape to increase aerodynamics, are mostly reserved for those people who have the time and drive to work on custom modifications.