Calculating your car’s fuel economy, also known as miles per gallon (MPG), can help you understand how efficiently your car uses fuel. Knowing your MPG can help you budget for fuel costs, compare vehicles, and drive in a more fuel-efficient manner. Here’s a step-by-step guide to calculating your car’s MPG.
What is MPG?
MPG stands for “miles per gallon” and it measures how far your car can travel on one gallon of fuel. It represents the fuel efficiency of your vehicle. The higher the MPG, the farther your car can go using the same amount of fuel.
For example, a car with a fuel economy of 30 MPG can drive 30 miles by using just one gallon of gasoline. A car that gets 10 MPG would only be able to drive 10 miles on a gallon.
Why calculate MPG?
There are a few key reasons to calculate your car’s MPG:
- Understand fuel efficiency – Calculating MPG helps you see how efficiently your car uses fuel compared to the EPA estimate or to other vehicles.
- Track fuel costs – Knowing your MPG allows you to estimate future fuel costs for trips and budget accordingly.
- Compare vehicles – MPG provides an apples-to-apples comparison of different models you may be considering.
- Adjust driving habits – Monitoring MPG over time can show how different driving styles and speeds affect fuel economy.
In short, MPG gives you valuable insight into how far you can drive and how much you’ll spend refueling your car. Checking your MPG periodically can help maximize efficiency.
How to Calculate MPG
Calculating your car’s MPG requires just two pieces of information:
1. The number of miles driven
2. The number of gallons of fuel used
Here is the basic formula:
MPG = Miles Driven / Gallons of Fuel Used
For example, if you drove 250 miles before refueling and it took 10 gallons to refill your tank, the equation would be:
250 Miles / 10 Gallons = 25 MPG
This means your car got 25 MPG for that tank of gas.
To get accurate MPG measurements, follow these steps:
1. Fill up your fuel tank completely
Make sure to top off your gas tank fully when you refuel. This gives you a consistent starting point for measurement.
2. Reset your trip odometer
Once you’ve finished filling up, reset your vehicle’s trip odometer to zero. This will track the miles driven on that tank of gas.
3. Drive normally until nearly empty
Drive as you typically would, under normal conditions, until the fuel tank is nearly empty. Avoid running the tank to completely empty, as that can damage the fuel system.
4. Fill up the tank again
Refill the gas tank fully and note the number of gallons it took to fill up.
5. Check the trip odometer reading
Your trip odometer now shows the miles that were driven on that tank of fuel.
6. Calculate MPG
Use the formula:
MPG = Miles Driven / Gallons Used
Plug in the miles from your trip odometer and the gallons used according to your fuel receipt. This will give you the MPG for that tank.
To increase accuracy, repeat this process over multiple fill-ups and average the MPG results. This helps account for variables like wind, terrain, engine load, and different driving styles.
Factors That Affect MPG
Your driving habits and vehicle condition can significantly impact MPG. Here are some of the factors that play a role:
Aggressive driving
Rapid acceleration and braking lowers MPG. Gentle acceleration and slowing down smoothly conserves fuel.
Speed
Driving at higher speeds, especially above 50 mph, reduces fuel economy. Optimal MPG is achieved between 30 to 50 mph.
Traffic conditions
Stop-and-go traffic and congestion waste fuel and lower MPG. Steady highway driving is most efficient.
Tire pressure
Make sure your tires are inflated to the proper tire pressure. Underinflated tires create more rolling resistance which reduces MPG.
Vehicle maintenance
Issues like worn spark plugs, dirty air filters, and old engine oil can decrease fuel efficiency. Regular maintenance keeps your car running efficiently.
Vehicle load
Added weight from passengers, cargo, or accessories like roof racks put more load on the engine, increasing fuel consumption. Remove unnecessary items to lighten the load.
A/C and heat use
Heating and cooling systems can draw engine power and reduce MPG, especially at low speeds. Try to limit use in stop-and-go traffic.
Vehicle aerodynamics
Wind resistance at highway speeds affects MPG. Roof racks or accessories that reduce streamlining should be removed when not in use.
Fuel type
Some vehicles can use regular gasoline, premium gasoline, or ethanol blends. Using the recommended octane helps optimize efficiency.
Engine temperature
A cold engine uses more fuel on start-up. Short trips before the engine fully warms up hurt MPG. Combine errands to allow adequate warm-up.
How to Improve Your Car’s MPG
With some simple changes, you can maximize your MPG and start saving money on fuel:
– Drive at moderate speeds between 30 to 50 mph
– Accelerate and brake gradually
– Reduce cargo weight and remove unnecessary roof racks
– Avoid excessive idling to warm up the engine
– Combine trips and errands to allow the engine to fully warm up
– Make sure tires are properly inflated
– Use the recommended motor oil and follow maintenance schedules
– Remove external add-ons like bug deflectors that affect aerodynamics
– Limit A/C and heat use at low speeds
– Follow the fuel type recommendation in your owner’s manual
Adopting fuel-efficient driving techniques takes practice but can become habit over time. Tracking your MPG as you try these changes helps reinforce good habits.
MPG FAQs
Here are answers to some common questions about calculating MPG:
How often should I calculate MPG?
Checking MPG with each fill-up is ideal. At minimum, calculate it once a month to track fuel economy over time.
Why is my MPG lower than the EPA estimate?
EPA ratings are based on laboratory tests. Real-world MPG is affected by driving behavior, conditions, and maintenance. Aggressive driving can lower MPG significantly.
How can I get better MPG in the city?
Frequent stopping and going in city driving hurts MPG. To improve, drive gently with gradual acceleration and braking. Combining trips also helps minimize engine warm-up periods.
Is premium fuel worth it for MPG?
Using a higher octane gasoline than your owner’s manual recommends offers no MPG benefit. Use the recommended regular, mid-grade or premium fuel.
Should I use trip A or trip B to calculate MPG?
It doesn’t matter as long as you use the same trip odometer consistently. Trip A and Trip B measure miles identically on most vehicles.
How can I increase highway MPG?
Highway MPG is maximized between 45-60 mph. When possible use cruise control to maintain steady speeds. Limit cargo weight and remove roof racks to reduce aerodynamic drag.
Sample MPG Calculation
Let’s walk through a sample MPG calculation:
Sarah has a crossover SUV that she primarily uses for her daily commute. She resets her trip odometer (Trip A) to 0 after filling up the tank. After driving for a full week, she refills the tank again.
Here are the details from her calculation:
- Miles driven according to Trip A: 358 miles
- Gallons it took to refill the tank: 13.6 gallons
To calculate her MPG, Sarah takes the miles driven and divides it by the gallons used:
MPG = Miles Driven / Gallons Used
MPG = 358 miles / 13.6 gallons
MPG = 26.3
Therefore, Sarah’s crossover SUV got 26.3 MPG over her daily commute that week. This is slightly lower than the EPA highway estimate of 28 MPG. Sarah realizes much of her commute involves stop-and-go traffic which likely reduced her fuel economy.
Sarah can continue tracking her MPG to look for trends and see if adjustments to her driving improve the numbers over time. Regular MPG calculations help owners maximize efficiency.
Using MPG Tracking Apps
Today there are mobile apps that can make MPG calculations even simpler. Popular gas mileage apps like Fuelly, Dash, and GasBuddy let you track fill-ups and mileage right from your smartphone.
Benefits of gas mileage tracker apps:
- Calculate MPG automatically using odometer photo capture
- Store fuel and mileage data over time
- Provide estimated fuel costs for trip planning
- Give reminders for maintenance based on mileage
- Report MPG trends in easy-to-read graphs
The convenience of gas mileage tracker apps encourages more frequent MPG measurement since all the information is logged digitally. Data can be exported for tax purposes or vehicle maintenance records.
Many MPG apps also include useful tools like station locators, fuel price comparisons, and digital versions of your vehicle’s owner’s manual. Test out a few options to see which gas mileage app fits your needs.
Conclusion
Calculating your car’s MPG is one of the best ways to monitor your vehicle’s fuel efficiency. Understanding your MPG helps you budget fuel costs, maximize efficiency, and even choose your next car. All it takes is a little simple math using miles driven and gallons used.
Try measuring MPG consistently with each fill-up. Look for patterns and ways you can tweak your driving to boost those numbers. Improving MPG by just 3-4 mpg can save significant fuel expenses over time. With gas prices constantly fluctuating, tracking your car’s MPG is a smart money-saving practice for any driver.
