How to save money on gas (and keep your gas budget on track)

The short answer: to save money on gas, burn less of it: drive smoothly, slow down a little on the highway, combine errands, keep tires properly inflated and buy only the octane your owner's manual calls for.

• Slowing down 5 to 10 mph averages a 7% to 14% benefit
• Aggressive driving can lower highway mileage by roughly 15% to 30%
• Short cold-start trips can use twice as much fuel as one longer trip
• Give gas its own budget line and track fill-ups for one month
• Next step: Plan it with the Vehicle Maintenance Log ($3.99).

The fastest way to save money on gas is to burn less of it: drive smoothly, slow down a little on the highway, combine errands into one trip, keep your tires properly inflated and buy only the octane your owner's manual calls for. Then give gas its own line in your budget and track every fill-up, so you can see the savings instead of guessing at them.

Most gas saving tips online stop at "use a gas app." Those can help, but a few cents off a gallon matters less than how many gallons you buy. This guide puts the tips in order of payoff, using the U.S. Department of Energy and EPA's FuelEconomy.gov testing, then shows you how to turn them into a gas budget you can actually stick to. Every dollar amount in our examples is hypothetical, so plug in your own numbers.

Want one place to write it all down? Our Vehicle Maintenance Log ($3.99, printable PDF) has a Fuel & MPG Log right next to the oil change and tire pages, so you can see your mileage and your maintenance on the same sheet.

Ways to save on gas, ranked by payoff

Here's what FuelEconomy.gov's testing found for the habits that matter most. Percentages are improvements (or losses) in gas mileage, so your actual dollar savings depend on how much you drive and what you pay per gallon.

The pattern is clear: the biggest wins are free and come from how and how much you drive. Car care adds smaller, steady gains on top.

Step 1: Find your real gas number

You can't save on gas if you don't know what it costs you now. Start with two numbers: your real miles per gallon (MPG) and your cost per mile.

To calculate your MPG at the pump:

1. Fill the tank completely and reset your trip odometer (or write down the odometer reading).
2. Drive normally until your next fill-up.
3. Fill the tank completely again and note how many gallons it took.
4. Divide the miles driven by the gallons. That's your real MPG.

Do this for three or four tanks in a row. One tank can be thrown off by a road trip or a week of snow, but a few tanks give you an honest average.

To find your cost per 100 miles, FuelEconomy.gov uses this formula: fuel price ÷ MPG × 100. Here's a hypothetical example:

That last row is the point: better habits lower your cost on every mile. If your household has two cars, drive the more efficient one when you can, which FuelEconomy.gov also suggests for commuting.

Step 2: Drive like there's a full cup in the cup holder

How you drive matters more than any coupon. FuelEconomy.gov's page on driving more efficiently says speeding, rapid acceleration and hard braking can lower your gas mileage by roughly 15% to 30% at highway speeds and 10% to 40% in stop-and-go traffic.

• Ease off the gas from a stop. Speed up gradually instead of racing to the next light.
• Look ahead. If the light up ahead is red, coast instead of driving fast and braking hard.
• Slow down on the highway. Gas mileage usually drops quickly above 50 mph. FuelEconomy.gov says you can think of each 5 mph over 50 as paying about $0.30 more per gallon, based on the $4.28 fuel price it uses for its estimates.
• Use cruise control on the highway. Holding a steady speed saves gas in most cases. Skip it on hilly or slick roads, where you need full control.
• Don't idle. Idling uses a quarter to a half gallon of fuel per hour, and restarting takes only about 10 seconds' worth of fuel. If you'll be parked for more than a minute, such as in a school pickup line or waiting outside a store, turn the engine off. FuelEconomy.gov suggests keeping engine starts to about 10 a day unless your car has a start-stop system.

If this feels like a lot, pick one habit for two weeks. Smooth starts are a good first choice because you do them dozens of times a day.

Step 3: Plan errands and routes around fewer trips

This is where the person who keeps the household calendar has a real advantage. FuelEconomy.gov's page on planning and combining trips explains that a cold engine is less efficient than a warm one, so several short trips from a cold start can use twice as much fuel as one longer, multipurpose trip covering the same distance.

A simple errand plan:

1. Keep one running errand list on the fridge or in your phone all week.
2. Pick one or two errand days. Group the pharmacy, post office, returns and grocery run into one loop.
3. Map the loop before you leave, so you aren't backtracking across town.
4. Attach errands to trips you already make, like work or practice drop-offs.
5. Plan meals for the week, so you're not making extra runs for one missing ingredient. Our guide on how to grocery shop on a budget helps here.

For your commute, FuelEconomy.gov suggests staggering your hours to miss rush hour, driving your most fuel-efficient vehicle, working from home if your employer allows it, and carpooling. Taking turns driving with others can cut your weekly fuel costs in half, and carpools can often use HOV lanes. Public transit is worth pricing out, too, if it's available and convenient.

Step 4: Car care that pays you back

Maintenance won't double your mileage, but it keeps you from losing money quietly. FuelEconomy.gov's page on keeping your vehicle in shape highlights these:

Use the tire pressure printed on the sticker in the driver's door jamb or in your owner's manual, not the maximum number on the tire's sidewall. The check engine light can be something as small as a loose gas cap, but have it looked at.

For full schedules, see our car maintenance checklist, plus our guides on how often to change oil and how often to rotate tires.

Step 5: Buy gas smarter

Once you're burning fewer gallons, then it's worth paying less for each one.

• Use the octane your manual requires. FuelEconomy.gov's guide to selecting the right octane fuel says most gasoline vehicles are designed to run on 87 octane. If your car doesn't require premium, you may get little to no benefit from it in normal driving. If your manual does require premium, use it, because lower octane can hurt the engine and may void your warranty.
• Compare prices before you're on empty. Prices can vary from station to station, so check a price app or note the cheapest stations on your regular routes. Don't drive miles out of your way to save a few cents.
• Check the cash price. Some stations post a lower price for cash than for cards. If you pay with a card, use one you pay off in full each month.
• Look at the rewards you already have. Many grocery and warehouse stores offer fuel discounts to members. Join only if you already shop there.
• Be skeptical of gas-saving gadgets. Products promising huge MPG gains rarely beat the free habits above.

Step 6: Give gas its own line in your budget

Gas is a variable expense: it changes every month with prices, weather and your calendar. That's why it's so easy to underestimate. Our guide to variable expenses explains how to plan for costs that move.

How to set your gas budget:

1. Add up the last three months of gas from your bank and card statements.
2. Divide by three for your monthly average.
3. Add a small cushion for price spikes and busy months.
4. Plan for known extras, like holiday travel, road trips or a new job with a longer drive.

Here's a hypothetical example:

If you like cash envelopes, a weekly gas amount works well with the cash envelope system. If you use a zero-based budget, gas gets its own line before the month starts. And whatever you save on gas should move somewhere on purpose, like savings or debt, or it disappears into other spending.

Plan the big car costs separately. Tires, repairs and holiday road trips aren't part of your weekly gas line. Use sinking funds to save a little each month for them. If you're driving to see family this season, our holiday travel budget for families lists every cost, from gas to tolls.

Step 7: Track fill-ups for one month

Tracking is what turns gas saving tips into real money. At every fill-up, write down:

• Date and odometer reading
• Gallons and price per gallon
• Total cost
• Your MPG since the last fill-up

After a month, compare your MPG with your Step 1 baseline. If it went up, the habits are working. If it didn't, check tire pressure and your driving speed first.

If you drive for work, keep a separate mileage log for taxes with the date, purpose and miles for each business trip. Personal fuel tracking and tax mileage records do different jobs.

Gas saving myths to skip

Why I plan this way

I grew up in Detroit as the oldest of three, in a working family that rebuilt after 2008. I was the one who kept track of who needed a ride and which form was due. A household runs on the same things a busy office does: lists, due dates and one shared calendar. Your gas budget is part of that calendar, because every extra trip shows up at the pump.

I also learned that slow progress is still progress. You don't need to master every tip this week. Pick one driving habit and one budget step, and build from there.

Tools to make it easier

To track mileage and maintenance in one place, the Vehicle Maintenance Log ($3.99) gives you a Fuel & MPG Log, a Mileage Log, an Oil Change Log, a Tire Log and a Maintenance Schedule. Print a set for each car and keep it in the glove box. Browse more logs and planners on our printables page.

To give gas its own line, the Zero-Based Budget Spreadsheet ($6.99, Excel and Google Sheets) has a "Left to budget" counter that turns green when every dollar, including gas, has a job. The Sinking Funds Tracker ($4.99) tells you how much to set aside each month for repairs, tires or a road trip. For the full set, the Ultimate Budget Bundle includes all six budget spreadsheets plus two printable planners for $19.99 instead of $46.42 bought separately. You can compare every option on our budget spreadsheets page.

For more everyday ideas beyond the car, see our list of ways how to save money, and our guide on how to lower monthly bills.

Start with your next fill-up. Write down the miles and the gallons. That one number tells you where your gas money is going.