Calculate MPG, track fuel efficiency, compare vehicles, and optimize your driving costs
Use cruise control on highways to maintain consistent speed
Gentle acceleration and braking significantly improves MPG
Under-inflated tires increase rolling resistance
Every 100 pounds reduces MPG by about 1%
Gas mileage, measured in Miles Per Gallon (MPG), tells you how far your vehicle can travel on one gallon of fuel. Understanding your actual fuel efficiency helps you budget for fuel costs, compare vehicles, and identify when your car may need maintenance.
MPG = Miles Driven / Gallons Used
Example: 300 miles / 10 gallons = 30 MPG
For the most accurate results, repeat this process over several fill-ups. Single-trip calculations can vary significantly based on driving conditions, traffic, weather, and terrain.
Hybrids, small efficient cars, and some diesels. Top 5% of vehicles on the road.
Compact cars, sedans, and efficient crossovers. Better than 75% of vehicles.
Most SUVs, midsize cars, and some trucks. Around the national average.
Large trucks, performance vehicles, and older cars. Consider efficiency improvements.
Divide the miles you drove by the gallons of fuel used. For example, if you drove 300 miles and used 10 gallons, your MPG is 300 ÷ 10 = 30 MPG. For accuracy, always fill your tank completely when measuring.
Generally, 30 MPG or higher is considered good, and 40+ MPG is excellent. The average US vehicle gets about 25.4 MPG. However, "good" depends on vehicle type—a pickup truck getting 25 MPG is actually quite efficient for its class.
EPA tests use standardized conditions that don't reflect real-world driving. Factors like aggressive acceleration, stop-and-go traffic, cold weather, AC use, cargo weight, and tire pressure all reduce actual fuel economy. Real-world MPG is typically 10-20% lower than EPA estimates.
Key improvements include: maintaining steady speeds (use cruise control), avoiding aggressive acceleration and braking, keeping tires properly inflated, removing excess weight, reducing idling, and keeping up with regular maintenance. These changes can improve MPG by 10-30%.
City MPG reflects stop-and-go driving with frequent braking and acceleration, which uses more fuel. Highway MPG represents steady-speed cruising, which is more efficient. Most vehicles get 20-30% better MPG on the highway. EPA combined ratings are 55% city, 45% highway weighted.
Yes, significantly. Most vehicles achieve peak efficiency between 45-65 mph. Above 50 mph, fuel economy drops rapidly due to increased air resistance—every 5 mph over 50 mph is like paying an extra $0.20/gallon. Driving 65 vs 75 mph can improve MPG by 10-15%.
To convert MPG to L/100km, divide 235.215 by your MPG. For example, 30 MPG = 235.215 ÷ 30 = 7.84 L/100km. Note that L/100km is an inverse scale—lower numbers mean better efficiency, opposite of MPG.
Yes, under-inflated tires increase rolling resistance and reduce MPG. For every 1 PSI drop in pressure across all tires, your gas mileage drops by about 0.2%. Keeping tires at the recommended pressure (found on the door jamb sticker) can improve MPG by 3% or more.
In-car MPG displays are typically within 5% of actual values but can be optimistic. For the most accurate reading, manually calculate MPG by dividing miles driven by actual gallons pumped over several fill-ups. This accounts for variations in driving conditions.
Only if your vehicle requires it. Premium gas (higher octane) prevents engine knock in high-compression engines but provides no efficiency benefit in cars designed for regular gas. Check your owner's manual— using premium when not required wastes money with no MPG improvement.
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