Are Stop-Start Engines More Efficient?

Fuel economy might be high on your list of priorities when you’re looking for a new car, and with this in mind, you may be wondering whether to choose a vehicle that features automatic stop-start technology. These systems are an increasingly common feature of cars, and they are marketed as fuel and emissions saving. But does the science stack up? Keep reading to find out how stop-start engines work, and whether they could help you to lower your driving costs and reduce your emissions.

How does stop-start technology work?

This technology does exactly what the name suggests. Featured in most modern cars, a stop-start system cuts the engine when a vehicle is stationary. It then restarts it when the brake is released, the clutch is engaged or the accelerator is pressed. The technology relies on an engine control unit to detect when the car is motionless or when it’s out of gear. In these situations, the fuel supply and spark to the engine are halted.

This process happens automatically, but if you have a car with one of these systems, you can choose to disable it. This is usually done by pressing a button displaying an ‘A’.

By switching the engine off automatically when you’ve stopped, for example when you’re waiting at traffic lights, junctions or in heavy traffic, the systems are designed to reduce the amount of fuel burned and make vehicles more environmentally friendly.

Cutting your fuel costs

So, the big question. Do they actually lower fuel costs? Well, according to research carried out by the American Automobile Association (AAA), yes they do. Tests conducted by the organisation found that fuel economy could be improved by up to seven per cent. The study looked at the performance of three stop-start vehicles in urban conditions to simulate a typical work commute, concluding that stop-start technology can deliver a “significant fuel economy benefit”.

Fuel savings of up to seven per cent can really add up over time, so using a car that features stop-start technology could help you to make major savings on your running costs. Exactly how much you’re able to save will depend on a range of factors, including your driving habits and the roads you tend to use. For example, if you often travel on congested urban routes where you’re likely to be stationary more of the time, you stand to make bigger savings than if you rack up most of your miles on motorways or other fast roads.

Reducing your car’s emissions

It’s not just the benefits to your wallet that you should think about when deciding whether to use stop-start technology. There are also environmental benefits to consider. A study by the Polytechnic University of Madrid compared the engine emissions of two four-wheel drive cars and found that the one fitted with automatic stop-start functionality recorded 20 per cent lower emissions than the vehicle without this technology.

The emissions lowering capability of stop-start systems is particularly important in towns and cities, where traffic is likely to be stationary for longer.

Other ways to drive more efficiently

As these points demonstrate, stop-start vehicle technology can play an important role in making your car cheaper to run and less polluting, but there are other ways to improve efficiency too. For example, you can:

Change your habits behind the wheel

The way you drive can have a surprisingly significant effect on how much fuel you burn. Harsh accelerating, for instance, can push up your fuel bill, as can driving quickly. Travelling at 70mph uses nearly 10 per cent more fuel on average than driving at 60mph. It’s a good idea to think about how you use air conditioning in your car too. This system causes your vehicle to burn more fuel, so when travelling at lower speeds, it’s generally recommended to switch it off and open your windows instead to keep the temperature down.

Lose unnecessary baggage

Do you have a habit of using your car as a dumping ground for anything from gardening tools to sports gear? If so, now’s the time to have a clear out. The heavier your vehicle is, the more fuel it will use. So, remove any items you don’t need before setting off on journeys. If you have a roof rack, think about taking it off when it’s empty too. This container might be a handy way to increase your storage capacity, but it also increases drag, making your car less efficient.

Choose your routes wisely

Before setting off on a new route, do some research into the best way to get to your destination. There might be a more direct route available than the one you initially think of. If possible, choose your travelling time wisely too. For example, if you can avoid travelling through congested areas at rush hour, do so.

Book regular services

Keeping your car in good condition is essential when it comes to maximising efficiency - and this is where regular servicing comes in. As well as helping to ensure that any problems are picked up early and are therefore easier and cheaper to fix, frequent servicing will mean your car will run as smoothly as possible. For example, regular oil changes and filter replacements, which are included as standard during vehicle services, will help to maximise fuel efficiency.

So, by choosing a car with stop-start technology, and paying attention to your driving habits and vehicle maintenance, you stand to make significant fuel and emissions savings.