How to improve fuel economy

How to improve fuel economy: every tip ranked by effect

Most lists of fuel economy tips give a 1% tip and a 30% tip the same weight. The table below ranks the common tips from the largest measured effect to the smallest, with the figure from the U.S. Department of Energy (fueleconomy.gov) or from Consumer Reports road tests next to each one.

The percentages are averages from tests on many vehicles, so a given car will land somewhere inside or near each range. The order matters more than the exact figure: driving habits and aerodynamics come first, maintenance second, and products sold as fuel savers last. As an example, take a car that uses 60 litres of petrol a month at £1.50 a litre, which is £90. A 10% improvement is worth about £9 a month.

Sources: Driving More Efficiently, Keeping Your Vehicle in Shape, fueleconomy.gov tips, Fuel Economy in Cold Weather, Consumer Reports (updated September 8, 2026), Federal Trade Commission (the US consumer protection agency). Checked October 2026.

Which driving habits save the most fuel?

Smooth driving is the single biggest lever on fuel economy. The U.S. Department of Energy reports that aggressive driving (speeding, rapid acceleration and hard braking) lowers fuel economy by roughly 15% to 30% at motorway speeds and 10% to 40% in stop-and-go traffic. Consumer Reports measured the same effect on the road: frequent hard acceleration and braking cut an older Toyota Camry's economy by 2 to 4 MPG (2 to 3 US MPG).

Smooth driving mostly means looking further ahead. Lifting off early and rolling toward a red light uses less fuel than holding speed and braking late, and a gap to the car in front lets you match the traffic instead of reacting to it. Every hard stop throws away fuel that was spent getting the car up to speed, and the next hard start spends it again.

• Accelerate gently. Press the pedal progressively and let the transmission shift up early. Full throttle from every light is the habit that costs the most in town.
• Anticipate stops. Coast toward lights, junctions and slow traffic in gear instead of braking at the last moment.
• Keep a steady speed. Small, constant speed changes on the motorway cost fuel too. On flat roads, cruise control holds speed more evenly than a foot, and fueleconomy.gov says it will save fuel in most cases.
• Use the instant MPG display. According to fueleconomy.gov, driver feedback displays help the average driver improve fuel economy by about 3%, and by about 10% for drivers who use them specifically to save fuel.

How much does speed affect fuel economy?

Fuel economy drops quickly above about 50 mph (80 km/h), because aerodynamic drag grows with speed. Slowing down by 5 mph to 10 mph on the motorway improves fuel economy by 7% to 14%, according to fueleconomy.gov, which in October 2026 expresses each 5 mph driven over 50 mph as paying about $0.31 more per US gallon, assuming fuel at $4.47 a US gallon (US figures). At a lower local price the money figure shrinks, but the percentage stays the same.

Consumer Reports tested two cars at steady speeds. Dropping from 65 to 55 mph raised fuel economy by 7 MPG in a Nissan Altima and 10 MPG in a Toyota RAV4 (6 and 8 US MPG), while cruising at 75 instead of 65 mph cost almost 8 MPG in the Altima and 7 MPG in the RAV4 (almost 7 and 6 US MPG). Consumer Reports also notes that over half of engine power at motorway speed goes to pushing air aside, which is why speed and roof loads matter so much.

What car maintenance improves fuel economy?

Correct tyre pressure, the right oil grade and fixing engine faults are the maintenance items with a measured effect on fuel economy. Each is small next to driving habits, but they add up, they cost little, and they also protect the car. A new air filter, the most common maintenance tip on dealer pages, does not improve fuel economy on a modern engine.

Tyres come first because they drift. Consumer Reports says tyres lose about 1 psi a month, and fueleconomy.gov puts the cost at about 0.2% of fuel economy for every 1 psi drop in the average pressure of all four tyres. Keeping them at the recommended pressure improves fuel economy by 0.6% on average and up to 3% in some cases. Use the pressure on the sticker in the driver's door frame, not the maximum printed on the tyre sidewall, and check the tyres cold. Rotation and balancing do not change fuel economy directly, but even wear keeps the tyres working as designed; see our guide to tyre rotation and balancing intervals.

Source: Keeping Your Vehicle in Shape, fueleconomy.gov, checked October 2026.

• Engine oil grade: fueleconomy.gov says the manufacturer's recommended grade improves fuel economy by 1% to 2%, and a thicker oil than the engine was designed for lowers it by about as much. The grade is in the owner's manual and often on the oil filler cap.
• Engine faults: fixing an out-of-tune engine improves its efficiency by 4% on average, according to fueleconomy.gov. A lit engine warning light is the usual sign; read the check engine code with an OBD2 scanner before guessing at parts.
• Air filter: on fuel-injected, computer-controlled petrol engines (early 1980s onward) and on diesels, replacing a clogged air filter does not improve fuel economy, although it can improve acceleration. Only older carburetted engines gain a few percent.

A 10-minute fuel economy check

This quick check covers every free or cheap item with a measured effect on fuel economy. It takes about ten minutes in a driveway with a tyre pressure gauge.

• Tyre pressure: set all four tyres, cold, to the pressure on the door-frame sticker.
• Engine warning light: if it is on, read the code before your next tank.
• Oil grade: compare the grade on your last oil change receipt with the owner's manual.
• Roof: take off the roof box, bike rack or empty crossbars if you are not using them this week.
• Boot: remove heavy items you carry for no reason. Every 100 lb (45 kg) costs about 1%.

How much do roof racks, weight and air conditioning cost in fuel economy?

A roof load costs far more fuel economy than extra weight or air conditioning. According to fueleconomy.gov, a large blunt rooftop cargo box reduces fuel economy by around 2% to 8% in city driving, 6% to 17% on the motorway and 10% to 25% at speeds of 65 to 75 mph. A rear-mount cargo box or tray costs only 1% to 2% in the city and 1% to 5% on the motorway.

Consumer Reports measured the same pattern. With two mountain bikes on the roof, a Nissan Altima fell from 55 to 40 MPG and a Toyota RAV4 from 47 to 38 MPG (46 to 33 and 39 to 32 US MPG). An empty roof rack alone cost 6 MPG in the Altima and 2 MPG in the RAV4, and a rooftop box cost 11 MPG and 6 MPG (9 and 5 US MPG). Bikes on a towbar-mounted rack still cost the Altima 14 MPG and the RAV4 6 MPG (12 and 5 US MPG), so a bike carrier is worth removing too.

Weight matters less: fueleconomy.gov estimates that an extra 100 pounds (45 kg) reduces fuel economy by about 1%, with smaller vehicles affected more than large ones. Air conditioning costs 1 to 5 MPG depending on the car (1 to 4 US MPG), according to Consumer Reports, which found no measurable fuel impact from opening the windows at 65 mph. Use the air conditioning when it is needed, and do not worry about windows on the motorway.

Does idling waste fuel?

Yes. Idling uses about 1 to 2 litres of fuel per hour (a quarter to a half US gallon), depending on engine size and air conditioning use, and it moves the car nowhere. According to fueleconomy.gov, restarting an engine takes only about ten seconds' worth of fuel, so turning the engine off for any stop longer than 1 minute saves money.

The same page adds a limit for cars without a start-stop system: keep engine starts to about ten a day on average, and drive at least 5 miles (8 km) between start cycles so the battery recharges. Cars with automatic start-stop are built for frequent restarts and handle this on their own. In winter, fueleconomy.gov advises against long warm-ups: most manufacturers recommend driving off gently after about 30 seconds.

Do fuel additives, premium petrol and fuel-saving gadgets work?

No product poured into the tank or plugged into the car has been shown to improve fuel economy significantly. The Federal Trade Commission reports that the EPA has evaluated or tested more than 100 alleged fuel-saving devices and has not found any product that significantly improves fuel economy. Some of these products may damage the engine or substantially increase exhaust emissions, and their ads usually claim savings of 12% to 25%.

Premium petrol only helps if the car requires it. Consumer Reports advises using premium only when the fuel flap or owner's manual says it is "required"; when it says "recommended" or nothing, regular is fine, and many cars get no significant performance or fuel economy benefit from higher octane. On September 8, 2026, premium averaged $5.03 a US gallon against $4.15 for regular (US figures), about $0.88 more per gallon for nothing in return.

Two related habits are worth keeping or dropping for the right reasons. Top Tier detergent petrol is about keeping the engine clean, and Consumer Reports recommends it without claiming an MPG gain. Filling up early in the morning to get denser fuel is a myth: underground tanks keep fuel temperature stable, and an 8°C (15°F) difference changes volume by only about 1%.

Why is fuel economy worse in winter?

Cold weather lowers fuel economy because a cold engine, cold fluids and short trips all burn more fuel. According to fueleconomy.gov, a conventional petrol car's fuel economy in city driving is roughly 15% lower at -7°C (20°F) than at 25°C (77°F), and it can drop as much as 24% on short trips of 3 to 4 miles (5 km to 6 km). Hybrids lose about 30% to 34% under the same conditions, and an electric vehicle's efficiency can drop roughly 39% in mixed driving.

Part of the winter loss can be recovered. The same page recommends parking in a garage or another warmer place, combining trips so the engine starts cold less often, driving off gently after about 30 seconds instead of idling to warm up, using seat heaters and defrosters only as needed, checking tyre pressure regularly (cold air lowers it), and removing roof racks when not in use. Compare winter fuel economy with last winter, not with last summer.

How to improve fuel economy in a truck, an older car, a hybrid or a motorcycle

The same physics applies to every vehicle: speed, smooth driving, aerodynamics, weight and tyre pressure. What changes is which of them matters most.

• Trucks and SUVs: a tall, square front makes speed and drag the dominant factors, so slowing down on the motorway pays off more than in a saloon. Racks, ladders and accessories mounted in the airstream add drag; take them off when not needed, keep heavy tools out of the bed when you are not working, and check the tyre pressure, which on large tyres drifts like any other.
• Older cars: an older car has more to gain from maintenance. Fixing an out-of-tune engine is worth about 4% on average, and on a carburetted engine a clogged air filter does cost a few percent of fuel economy, unlike on modern fuel injection.
• Hybrids: anticipation matters even more, because gentle braking lets regenerative braking recover energy that hard braking sends to the brake pads. Hybrids also lose more in winter, about 30% to 34% at -7°C (20°F) according to fueleconomy.gov. Our guide to hybrid car maintenance covers the rest.
• Motorcycles: riding position and luggage act like a roof box, so a tucked posture and no top case at motorway speed help. A dry or loose chain wastes power at the rear wheel; see our guide to motorcycle chain maintenance. Tyre pressure matters as much as on a car.
• Electric vehicles: the same habits extend range. EV efficiency is measured in miles per kWh or kWh per 100 miles, and cold weather hits it hardest, so preheat the cabin while plugged in, as fueleconomy.gov recommends.

What is hypermiling, and is it worth it?

Hypermiling is driving with techniques aimed at getting the maximum possible fuel economy from a vehicle. Its safe core is exactly what the data in this guide supports: anticipate traffic, accelerate gently, keep a steady and legal speed, avoid idling and keep the car light and well maintained. Those habits are worth adopting by anyone.

Some hypermiling tricks trade safety for a few drops of fuel and are not worth it: following close behind lorries to sit in their slipstream, switching the engine off while rolling, coasting in neutral, or rolling through stop signs to avoid restarting from zero. They remove your margin to react, can disable power steering and brake assistance, or break traffic law. The gain from the safe habits is already most of what hypermiling can deliver.

How do you know if your fuel economy actually improved?

Measure fuel economy tank to tank before and after a change, over at least three full tanks each. Fill the tank to the first click, reset the trip meter, drive normally, fill to the first click again, and divide the miles driven by the gallons it took to refill (litres ÷ 4.546). The full method, with partial fills and correct averages, is in our guide on how to calculate fuel economy tank to tank.

Compare like with like. Weather alone moves fuel economy by 15% or more, so compare tanks from the same season with similar routes, and average by total miles divided by total gallons rather than averaging per-tank figures. Trust the calculation over the dashboard reading, which is an estimate from engine data rather than a measurement of the fuel you bought.

WrenchTime, an iOS app for logging fuel, maintenance and trips for cars and motorcycles, does the tank-to-tank math for you. You mark each fill-up as a full tank or not, so consumption is computed between full tanks; a missed fill-up flag keeps a forgotten entry from producing an impossible figure; and efficiency drop alerts tell you when economy falls against your own history. Fuel grade tracking shows whether premium returns anything in your car, and recorded trips count hard braking and acceleration events, so you can check whether your driving is getting smoother. The fuel economy tracker guide covers how it computes each figure.

Key takeaways: how to improve fuel economy

The tips that move fuel economy, in order of effect, and the ones to skip.

• Drive smoothly first: aggressive driving costs 15% to 30% on the motorway and 10% to 40% in town, per fueleconomy.gov.
• Slow down above 50 mph: 5 mph to 10 mph less saves 7% to 14%.
• Take off roof loads: a large roof box costs 10% to 25% at 65 to 75 mph.
• Maintain the basics: door-frame sticker tyre pressure (up to 3%), the recommended oil grade (1% to 2%) and engine faults fixed (about 4%).
• Skip the myths: gadgets and additives, premium fuel the car does not require, morning fill-ups and new air filters on fuel-injected engines.
• Measure it: compare at least three full tanks before and after, in the same season.

See which tips work on your car

The only fuel economy figure that matters is your own. Log your next few fill-ups in WrenchTime, mark the full tanks, and the app shows your tank-to-tank economy and its trend, so a lower motorway speed or a tyre top-up shows up as a number instead of a feeling. The free version covers 1 vehicle with 3 fuel entries per month, and WrenchTime Pro removes those limits. The fuel economy tracker guide explains the details.