What are mild-hybrids? | AA Cars

Electrification is abuzzword in the car world right now, with manufacturers rushing to launch new electric, hybrid and plug-in hybrid models. 

But amidst these powertrains, firms are finding ways to give life to regular petrol and diesel models with what’s known as mild-hybrid technology. 

Here’s what you need to know.

What is a mild-hybrid? 

Mild-hybrid technology essentially pairs existing petrol and diesel engines with a small electric motor, which works as an advanced stop/start system. It means that the engine can switch off when you’re coasting or slowing. 

However, some firms utilise this tech to power electrical functions within the car –  the touchscreen, for example. The setups vary depending on the size of the system used and what it’s used for. 

Other firms use mild-hybrid technology to provide additional torque and smoothness through the electrical assistance. More powerful systems mean the car’s engine can be turned off for an extended period (up to 40 seconds) when coasting, before the starter generator is automatically utilised when acceleration is needed again.  

What’s the difference between a mild-hybrid and a regular hybrid powertrain? 

It might not sound like it, but a mild-hybrid system is much simpler than a regular hybrid, and they’re easier to develop and make available on a wide number of models. It’s why manufacturers often roll the tech out across their range of models, rather than just make it available on the odd car. It’s also cheaper, which is why it’s being used more often.  

However, unlike a hybrid, mild-hybrids can rarely just run on electricity. Instead, the system is there simply to provide assistance and efficiency to the engine. 

What are the benefits of mild-hybrids? 

There are several benefits to this technology, depending on the manufacturer. The first is efficiency. Mild-hybrids add assistance and coasting functions, leading to less strain on the engine.  The significance of this benefit depends on the manufacturer, but the difference is usually quite small. 

Let’s use the Ford Puma as an example, which has a 123bhp 1.0-litre petrol engine available with or without the tech. In regular form, the model can return 48.7mpg and CO2 emissions of 132g/km. With the mild-hybrid, the fuel economy increases to 51.3mpg, and emissions drop to 125g/km. So although this seems like a small benefit, it would add up over the years. 

Mild torque and responsiveness benefits are another perk – the mild-hybrid Puma gains 40Nm more torque with the technology. However, in terms of figures, this only drops the 0-60mph time by a tiny 0.2 seconds. 

The best way of thinking about the benefits of mild-hybrid is that it’s a small bonus but one that brings no compromise – it’s usually so light that you’ll forget it’s there. It’s often quite inexpensive, too. On the Puma, it adds a rather minor £280 to the asking price. 

Which firms offer mild-hybrids? 

Audi was one of the first to show this technology in 2016, on the SQ7. Since then, most of the firm’s diesel models are mild-hybrids . 

But outside of Audi, most manufacturers  offer the system. Some have made it available on selected versions of certain models, whereas others have it as standard on models – all Mazda2, Mazda3 and Mazda CX-30 versions feature the tech, for example.  Ford is increasingly using mild-hybrid, and Volvo and Mercedes offer it on plenty of their models.


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