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. Stop-start is a system on most modern cars that cuts the engine when the car is stationary in order to reduce fuel consumption and emissions. 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. The system uses a computer to detect when the car is stationary or out of gear, or when it’s running in low-load conditions; at which point it halts fuel delivery and spark to the engine.
In the case of hybrid cars, a limited amount of torque can be supplied by the car’s electric drive motor while the engine is off, although it’s usually only enough to maintain speed on a level grade or around town. The ignition starts again when the car begins moving, the clutch is pressed or more power is needed.
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? According to research, the answer is yes. Tests conducted by the American Automobile Association (AAA) 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 that compared the engine emissions of two four-wheel drive cars 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:

Driving style
There’s no doubt that the speed you drive at is arguably the most influential factor affecting fuel consumption. Adopting bad driving habits such as speeding and excessive acceleration will drain fuel. There are a number of ways you can change your driving habits to have a significant impact on the money you spend at the pump, such as using cruise control which helps to maintain a constant speed and make the best use of your fuel. Sudden braking will also have a detrimental effect on your MPG, so making sure you leave enough distance between yourself and the car in front whilst driving will mean you’re not constantly hitting the brake pedal.

Lighten the load
The heavier the vehicle, the more fuel it will need to keep it moving, especially when driving in stop-start traffic.
On average an extra 50kg of weight in a vehicle will increase fuel consumption by 1-2%, so whilst it can be easy to get in the habit of using your car as a storage space, it’s best to only carry the essentials.

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.

Servicing
Maintaining your vehicle is one of the best ways to ensure your car runs efficiently and stays in good shape. From checking brakes to regular oil changes, a full service can reduce the burden on your engine and help to provide improved miles per gallon.

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.