How to Check Fuel Economy on a Used Car Before You Buy

What the fuel economy numbers mean on a used car

The fuel economy of a used car tells you how many miles it will travel on one gallon of gas. You will see two numbers: city mileage (driving with frequent stops) and highway mileage (steady-speed driving). A car that gets 22 city / 28 highway means it travels 22 miles per gallon in the city and 28 miles per gallon on the highway.

These numbers come from standardized tests run by the EPA (Environmental Protection Agency), not from what the dealer claims or what the previous owner experienced. The actual mileage you get depends on how you drive, the condition of the car, and whether you maintain it properly. A well-maintained car will perform closer to the EPA estimate; a neglected one will fall short.

The difference between city and highway matters for your wallet. If you spend most of your time in stop-and-go traffic, the city number is what you will actually see. If you drive mostly on interstates, the highway number is more relevant to your real-world costs.

Key Takeaways

• The EPA fuel economy label shows city and highway mileage separately, and you can find these numbers on the Monroney sticker, the car's window label, or fueleconomy.gov.
• Actual fuel economy depends on driving habits, maintenance, tire pressure, and road conditions — the EPA estimate is a baseline, not a may provide.
• Older used cars (pre-2007) may not have EPA estimates available, so you can research similar models or ask the dealer for records of the previous owner's fuel costs.
• Comparing fuel economy across multiple used cars of the same year and model helps you spot a vehicle that is running poorly and may need expensive repairs.
• A car with significantly worse fuel economy than its EPA rating suggests mechanical problems like a failing oxygen sensor, clogged air filter, or misaligned wheels.

Where to find the fuel economy number for a specific used car

The easiest place to look is fueleconomy.gov, the official EPA website. Enter the year, make, and model of the car you are considering, and the site will show you the EPA city and highway estimates, plus an annual fuel cost estimate based on current gas prices. This number updates regularly, so the cost shown today may differ from what you see in a month.

If you are at the dealership or looking at a private sale, check the car's window sticker (called the Monroney label). This label is required on all new cars and many used cars still have it. It displays the EPA estimates, the vehicle's VIN, and the dealer's asking price. If the sticker is missing, ask the dealer or seller for it — they may have it on file.

For cars older than 2007, fueleconomy.gov may not have specific data. In that case, search for the model year and engine size on the site to find similar vehicles, or ask the previous owner (if you can reach them) whether they kept fuel receipts or maintenance records showing actual consumption over time.

How to spot a used car with fuel economy problems

Compare the car's actual fuel economy to its EPA rating by asking the seller or dealer for maintenance records. Some sellers track their fuel costs and mileage; others do not. If records exist, divide the total miles driven by the total gallons used to calculate real-world mileage. If the number is significantly lower than the EPA estimate — say, 5 or more miles per gallon worse — the car may have a mechanical issue.

Common problems that reduce fuel economy include a faulty oxygen sensor (which tells the engine how much fuel to burn), a clogged air filter (which restricts airflow and forces the engine to work harder), worn spark plugs, misaligned wheels, or underinflated tires. A pre-purchase inspection by a trusted mechanic can identify these issues before you buy. The cost of that inspection (usually $100 to $200) is worth it if it saves you from buying a car that will drain your gas tank.

Also check the tire pressure. Underinflated tires increase rolling resistance and reduce fuel economy by up to 3 percent per 1 PSI (pound per square inch) below the recommended pressure. The correct pressure is printed on a sticker inside the driver's door frame, not on the tire itself. If the tires are soft, that may be a quick fix — or a sign the car has not been well maintained.

How driving habits affect real-world fuel economy

The EPA estimates assume a mix of city and highway driving at moderate speeds. Your actual mileage will differ based on how you drive. Aggressive acceleration, hard braking, and speeding all burn more fuel. Idling, towing, and driving in cold weather also reduce fuel economy. If you drive aggressively or in heavy traffic most days, expect to see 10 to 20 percent worse mileage than the EPA estimate.

Conversely, smooth acceleration, steady speeds, and highway driving can sometimes match or exceed the EPA estimate. Hypermiling — deliberately driving to maximize fuel economy — can push mileage higher, but it is not a realistic long-term strategy for most drivers.

The weight you carry matters too. A full trunk or roof rack adds drag and weight, both of which increase fuel consumption. Removing unnecessary cargo can improve your mileage by 1 to 2 percent per 100 pounds removed.

Comparing fuel economy across used cars to find the best value

If you are deciding between two or three used cars, calculate the annual fuel cost for each one. Multiply your estimated annual miles by the EPA combined rating (a blend of city and highway), then divide by the current gas price. For example, if you drive 12,000 miles per year, a car rated at 25 MPG, and gas costs $3.50 per gallon, your annual fuel cost is roughly $1,680.

A car with 30 MPG would cost about $1,400 per year in fuel — a savings of $280 annually. Over five years, that is $1,400 in fuel savings, which may offset a higher purchase price. A car with 20 MPG would cost $2,100 per year, or $700 more than the 25 MPG car. These differences add up, especially if you drive more than 12,000 miles per year.

Do not assume that a newer used car always has better fuel economy than an older one. Fuel economy improved significantly between 2007 and 2015, but a 2010 model may be just as efficient as a 2015 model of the same make and model. Compare the specific year and engine size, not just the age.

How maintenance affects fuel economy over time

A used car's fuel economy will decline gradually as it ages if maintenance is neglected. Regular oil changes, air filter replacements, and spark plug service keep the engine running efficiently. Skipping these tasks forces the engine to work harder and burn more fuel.

Before buying a used car, ask for service records showing oil changes, filter replacements, and any major repairs. A car with a complete maintenance history is more likely to deliver fuel economy close to the EPA estimate. A car with gaps in the service record may have hidden problems that will cost you money at the pump.

After you buy, keep up with the manufacturer's recommended maintenance schedule. Check tire pressure monthly, replace the air filter every 12,000 to 15,000 miles (or as recommended), and use the correct grade of motor oil. These simple steps will help your used car maintain its fuel economy and run reliably.

Frequently Asked Questions

Can I trust the EPA fuel economy number for a used car?

The EPA number is a reliable baseline for comparing cars, but your actual mileage will vary based on driving habits, maintenance, and road conditions. Think of it as a starting point, not a promise. A well-maintained car driven smoothly will come close to the EPA estimate; a neglected car or aggressive driver will see worse results.

What if the used car I want does not have a fuel economy label?

Search fueleconomy.gov by year, make, and model to find the EPA estimate. If the car is older than 2007 and the site does not have data, look up similar models from that year or ask a mechanic familiar with that vehicle what real-world mileage owners typically report.

Does a hybrid or electric used car always cost less to fuel than a gas car?

Hybrids typically cost less to fuel than comparable gas cars, especially in city driving. Electric cars have lower per-mile energy costs, but the total cost depends on your local electricity rates. Compare the EPA estimates and your local fuel prices for an accurate picture of what you will actually spend.

Should I pay more for a used car with better fuel economy?

Calculate the annual fuel savings and compare it to the price difference. If a car costs $2,000 more but saves you $300 per year in fuel, it will take about seven years to break even. If you plan to keep the car longer than that, the better fuel economy may be worth the higher price.

What should I do if a used car gets much worse mileage than the EPA estimate?

Have a mechanic inspect it before you buy. Poor fuel economy often signals fixable problems like a clogged air filter, bad oxygen sensor, or underinflated tires. If the inspection reveals major engine issues, factor the repair cost into your decision or walk away from the deal.