How to save fuel – the ultimate guide

The cost of fuel is always a hot topic with motorists, which is why our very own RAC Fuel Watch team monitor it on a daily basis.

Although the ever-increasing price of petrol or diesel is something beyond our control, there are some surprisingly simple ways to save fuel - rewarding your wallet and the environment.

Buying a more fuel efficient car is one way, but not everybody has the money for a new car. To help drivers save money at the pumps, we've compiled the ultimate guide to making your current car more economical.

From speed to driving style and even keeping up with maintenance, here are 10 ways you can change your driving habits and save money.

Top 10 ways to save fuel: a guide

1. Make sure you maintain your vehicle

Regular maintenance and servicing improves the efficiency of your vehicle, and therefore can improve your fuel consumption. Getting your car serviced regularly is advised, and a RAC Mobile Mechanic can help, or search for one of our RAC Approved Garages.

It’s particularly important to check your tyre pressures and make sure they are inflated correctly, as indicated in your owner’s manual, as underinflated and overinflated tyres both adversely affect fuel economy. Tyre pressures will vary depending on the load you are carrying: if you have four passengers and luggage then you will need your tyres inflated to the maximum recommended pressures.

Below is a short video on important maintenance checks you should regularly carry out. 

2. Speed: know when to accelerate

It should go without saying, but the higher your speed and the more you accelerate, the more fuel your car uses. Excessive speed is by far and away the biggest factor reducing your car's fuel economy.

Obviously you should stick to the speed limits at a minimum, but you shouldn't be afraid to sit below the limit - it's not a target.

Drive to the conditions, too. If a 60mph speed limit road is narrow and full of potential hazards, it makes sense to keep your speed at a controlled level rather than accelerating and braking constantly.

This optimum fuel economy speed will be different for every car, but when the RAC completed its Record Road Trip in the Audi A6 ultra, that particular car’s optimum fuel economy speed was 52mph in seventh gear on the flat.

While there is an ideal speed, road conditions and gradients don’t often allow you to do that speed so you have to improvise and learn to adjust your driving according to the road ahead, a technique often referred to as hypermiling.

Generally speaking, there is no one driving speed which is optimum for fuel economy.

Over the years the speed of 56mph has often been talked about as being the optimum speed. This was due to the old fuel consumption test being run at three speeds: urban, 56mph and 75mph – and 56mph was always, unsurprisingly, the most efficient of these. Typically, cars are most efficient at 45-50mph. 

3. Highest gear possible within the speed limit

While accelerating gently is good for economical driving, there is a balance. Constantly accelerating gradually isn't the best way to save fuel, most experts agree.

Instead, the best advice is to get up through the gears to your desired speed relatively quickly. That doesn't mean floor it and use all the revs, but a decent rate of acceleration allows you to reach a set cruising speed and high gear where your engine can be at its most efficient. That doesn't always apply in urban environments, though, because you'll likely have to slow down again quite quickly.

Probably the biggest secret to achieving high mpg is driving in the highest possible gear for your vehicle while keeping within the speed limit. Remember: the faster an engine spins, the more fuel it uses. With that in mind, find the balance between letting revs climb too high and letting them drop too low, where your engine starts to labour and could stall.

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As well as fuel economy differing from vehicle to vehicle, it is also dependent on a number of other factors such as tyre pressure, presence of roof racks, and driving style – all of which are covered in this guide.

4. Anticipate: try not to lose momentum

In line with the above point, keeping the car moving at the right speed is essential to fuel economy. Obviously, this depends on traffic conditions and what’s happening on the road ahead, but slowing down and having to accelerate again naturally uses more fuel.

The best advice is to drive as smoothly as possible, gently using the steering, accelerator and brakes. When slowing down, it’s important to remain in gear as the fuel cut-off switch in a fuel injection engine is then activated, meaning virtually no fuel is used while braking.

Try to anticipate what’s going to happen in front of you by looking well ahead. This way you’ll see the traffic lights on red meaning you can ease back on the accelerator or slow down naturally and potentially keep moving as opposed to coming to a stop. Similarly, lift off the accelerator way in advance of a tight bend to avoid excessive braking.

Driving up hills destroys fuel economy. When you spot a hill coming try to accelerate a little before you reach it (within the speed limit, of course) then ease off as you drive up. The extra momentum should be enough to minimise additional fuel consumption.

5. Does cruise control use more fuel?

Cruise control only aids fuel economy when driving on a constant flat surface, hence why it is usually best reserved for motorway driving.

One of the keys to saving fuel is driving at a constant speed, cruise control can do this effectively on flat surfaces, making your driving as fuel efficient as possible by negating unnecessary acceleration.

However, if you were to use your cruise control regularly, not on flat roads, you would encounter problems that would increase your fuel consumption.

This is because your cruise control would be slower to react to gradient changes, meaning when reaching the brow of a hill – at which point you would normally take your foot off the accelerator to maintain more of a constant speed when descending – your cruise control will keep the power on for a little longer as it’s unable to see the gradient change in front of you. Driving in this way regularly would lead to worse fuel consumption.

Interestingly, the most fuel-efficient roads in the country are not quiet extra-urban dual carriageways or 20mph city streets, they are motorways. This is where you can leave the car in top gear and gently cruise along, using minimal fuel.

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6. Don’t get dragged down

Don’t leave your roof bars and roof box on because they create wind resistance and cause your car to use more fuel through the ‘drag’ effect. This is increased the faster you drive.

According to the Energy Saving Trust an empty roof rack adds 16% drag when driving at 75mph. At the same speed a roof box adds 39%, making your vehicle much less fuel efficient. 

Even those little flags you can affix to your vehicle to show support for your football team during the world cup can decrease your mpg.

Driving with an open window also has a similar effect.

7. Does the AC and heat use fuel?

Yes, it does. Don’t use your air conditioning unless you really have to as it uses engine power and therefore increases fuel consumption - this is more of a problem in older cars than the newest, most efficient air-con systems.

This goes for heat as well as cooling, so try to dress for the weather, even inside your car, if fuel efficiency is a big concern.

8. Combine journeys: a warm engine is more efficient

Consider making one round trip rather than several short trips. Once the engine is warm it will operate at its most efficient whereas several cold starts will increase fuel consumption even though the total mileage could be the same

This is why the RAC’s Record Road Trip team kept going almost continuously, only stopping for 20 minutes at a time on the way to setting a world record of driving through 14 countries on one tank of fuel. That was 1,158.9 miles, driving at an average speed of 45mph and achieving an incredible 75.9mpg.

Visit the RAC Route Planner to help plan your journey in a more fuel-efficient way.

9. Lighten the load

While this isn’t going to make the biggest difference to your mpg figures it stands to reason that the heavier a vehicle is, the more fuel it will use.

For that reason, don’t keep unnecessary items in your boot as they all add weight to your vehicle, which is not going to help your fuel economy in the long run.

10. Use the technology

Stop-start is a feature found in almost every petrol and diesel car made in the last few years. It's also a controversial one, with many drivers finding it annoying and disabling it.

But, used correctly, stop-start really can save you fuel. Most experts agree that if you are going to be stationary for 10 seconds or more, then letting your engine shut off and restart is more fuel efficient than leaving it idling.

The average family car can use up to half a gallon of fuel per hour when left idling - enough to travel around 25 miles.

What is hypermiling?

In light of fuel cost increases, the technique of hypermiling has been gaining popularity as fuel economy best practice.

Whilst it's got a flashy name, simply following the tips above will save you money on fuel, so don't worry too much about sticking to a specific hypermiling regimen.