Calculate your car's MPG (miles per gallon) and estimate fuel costs for trips. Track and improve your fuel efficiency.
Track MPG over multiple fill-ups for a more accurate average.
Miles per gallon (MPG) measures how far your car travels on one gallon of fuel:
For example, if you drove 350 miles and used 12 gallons of gas, your fuel economy is 350 ÷ 12 = 29.2 MPG.
For accurate MPG tracking, use the fill-up method:
Repeat this process several times and average the results for a reliable estimate. Single fill-up calculations can vary due to pump differences and how full the tank was.
To estimate fuel cost for any trip:
Example: Planning a 300-mile trip at 25 MPG with $3.50/gal gas:
For round trips, double the distance. For multi-day road trips, factor in estimated daily driving distances to plan fuel stops and budget accordingly.
| Vehicle Type | Average MPG | Annual Fuel Cost* |
|---|---|---|
| Compact car | 30-35 | $1,400-1,600 |
| Midsize sedan | 25-32 | $1,500-1,900 |
| Full-size sedan | 22-28 | $1,700-2,200 |
| SUV | 20-28 | $1,700-2,400 |
| Pickup truck | 17-24 | $2,000-2,800 |
| Minivan | 20-25 | $1,900-2,400 |
| Hybrid | 40-55 | $900-1,200 |
| Electric (MPGe) | 100-130 | $500-700 |
*Based on 12,000 miles/year and $3.50/gallon (or equivalent electricity cost)
The EPA tests all new vehicles using standardized procedures. When shopping for a car, you'll see:
| Rating | What It Measures |
|---|---|
| City MPG | Stop-and-go urban driving |
| Highway MPG | Steady-speed highway driving |
| Combined MPG | Weighted average (55% city, 45% highway) |
Real-world vs. EPA estimates: Most drivers get 10-20% lower MPG than EPA ratings. The EPA tests in controlled conditions without A/C, with moderate acceleration, and at lower speeds than typical highway driving. Your driving style, terrain, and climate all affect actual results.
Highway driving is typically 20-30% more fuel efficient than city driving:
| Driving Type | Characteristics | Fuel Impact |
|---|---|---|
| City | Frequent stops, idling at lights, acceleration from stops | Uses most fuel |
| Highway | Steady speed, minimal braking, consistent throttle | Most efficient |
| Combined | Mix of both driving types | EPA weighted average |
The efficiency gap is largest for conventional vehicles and smallest for hybrids, which recapture energy during braking.
Your driving style has the biggest impact on fuel economy—potentially varying MPG by 30% or more:
Regular maintenance directly impacts fuel economy:
Extra weight forces the engine to work harder:
Conditions outside your control also affect fuel economy:
Fuel economy varies significantly by season:
| Season | MPG Impact | Primary Causes |
|---|---|---|
| Winter | -10% to -20% | Cold engine, winter fuel, tire pressure, A/C defrost |
| Spring/Fall | Baseline | Moderate temperatures, optimal conditions |
| Summer | -5% to -10% | A/C usage, summer fuel blends |
Winter driving is hardest on fuel economy. Short trips in cold weather are especially inefficient since the engine never fully warms up.
Understanding yearly costs helps when comparing vehicles or evaluating upgrades:
| MPG | Gallons/Year* | Annual Cost** |
|---|---|---|
| 15 | 1,000 | $3,500 |
| 20 | 750 | $2,625 |
| 25 | 600 | $2,100 |
| 30 | 500 | $1,750 |
| 35 | 429 | $1,500 |
| 40 | 375 | $1,312 |
| 50 | 300 | $1,050 |
*Based on 15,000 miles/year **Based on $3.50/gallon
For typical commutes (22 working days per month):
| Daily Round Trip | MPG | Gas Price | Monthly Cost | Annual Cost |
|---|---|---|---|---|
| 20 miles | 25 | $3.50 | $62 | $739 |
| 30 miles | 25 | $3.50 | $92 | $1,108 |
| 40 miles | 25 | $3.50 | $123 | $1,478 |
| 50 miles | 25 | $3.50 | $154 | $1,848 |
| 50 miles | 35 | $3.50 | $110 | $1,320 |
| 50 miles | 45 | $3.50 | $86 | $1,027 |
Improving from 25 to 35 MPG saves 528/year) on a 50-mile daily round-trip commute.
MPG is intuitive but can be misleading when comparing fuel savings. Gallons per 100 miles shows the actual fuel consumed:
| MPG | Gallons per 100 Miles | Savings vs. Next Lower |
|---|---|---|
| 10 | 10.00 | - |
| 15 | 6.67 | 3.33 gallons |
| 20 | 5.00 | 1.67 gallons |
| 25 | 4.00 | 1.00 gallons |
| 30 | 3.33 | 0.67 gallons |
| 40 | 2.50 | 0.83 gallons |
| 50 | 2.00 | 0.50 gallons |
Key insight: Upgrading from 15 to 20 MPG saves more fuel (1.67 gal/100mi) than upgrading from 35 to 50 MPG (0.83 gal/100mi). This is why replacing gas guzzlers provides the biggest environmental and economic benefit.
Most countries use liters per 100 kilometers (L/100km):
| US (MPG) | L/100km | Efficiency Level |
|---|---|---|
| 20 | 11.8 | Below average |
| 25 | 9.4 | Average |
| 30 | 7.8 | Good |
| 35 | 6.7 | Very good |
| 40 | 5.9 | Excellent |
| 50 | 4.7 | Exceptional |
Note: In L/100km, lower numbers indicate better efficiency (opposite of MPG).
UK gallons are larger than US gallons, so UK MPG figures are about 20% higher for the same efficiency. Multiply US MPG by 1.201 to convert to UK MPG.
EVs use MPGe (miles per gallon equivalent) to compare with gas vehicles:
33.7 kWh equals the energy content of one gallon of gasoline.
| EV Efficiency | MPGe | Comparison |
|---|---|---|
| 0.25 kWh/mile | 135 | Very efficient EV |
| 0.30 kWh/mile | 112 | Typical EV |
| 0.35 kWh/mile | 96 | Larger EV/SUV |
| 0.40 kWh/mile | 84 | Electric truck |
Cost comparison: At 3.50/gallon gas, an EV getting 100 MPGe costs about 0.14/mile for a 25 MPG gas car—roughly 10x cheaper to fuel.
Using the right fuel grade matters:
| Octane | Use When | Effect of Wrong Choice |
|---|---|---|
| Regular (87) | Manufacturer recommends | Using premium wastes money |
| Mid-grade (89) | Manufacturer recommends or requires | Marginal benefit if not required |
| Premium (91-93) | Required by manufacturer | Using regular may cause knocking and reduced performance |
Modern engines with knock sensors can adjust timing for lower octane fuel, but you'll lose some power and efficiency. Only use premium if your vehicle requires it—"recommended" means optional.
Myth: Premium gas improves MPG in regular-fuel cars Reality: Unless your engine requires premium, you're just spending more money for no benefit.
Myth: Warming up the engine improves efficiency Reality: Modern fuel-injected engines need only 30 seconds. Extended idling wastes fuel.
Myth: A/C always uses less fuel than open windows Reality: At low speeds, open windows are more efficient. At highway speeds, A/C is better due to aerodynamic drag from open windows.
Myth: Fuel additives significantly improve MPG Reality: Most additives provide minimal measurable improvement. Stick to quality fuel and proper maintenance.
Myth: Manual transmissions always get better MPG Reality: Modern automatics with 8+ speeds often match or beat manual efficiency.
Calculate whether a more efficient vehicle makes financial sense:
Example: Driving 15,000 miles/year at $3.50/gallon, upgrading from 20 MPG to 35 MPG:
If the more efficient car costs $8,000 more, payback takes about 7 years from fuel savings alone. Factor in resale value, maintenance costs, and other benefits when deciding.