The real petrol usage of plug-in hybrids in South Africa

Plug-in hybrid (PHEV) cars often boast impossibly frugal fuel consumption figures, sometimes as low as 0.7l/100km for an SUV teetering on three tonnes that can still rocket to 100km/h in 5.5 seconds.

This, however, is a rather misleading figure.

PHEVs are a complicated technology that sees an internal combustion engine working in partnership with a proper electric motor and battery to drive the wheels.

The electric part of the powertrain is usually significantly larger than what you’ll find on a mild-hybrid (MHEV) or traditional hybrid (HEV) vehicle, allowing the PHEV to drive on electricity alone for decent distances and generous speeds without tapping into the petrol or diesel block.

Automakers thus assume, or imply, that most people will largely complete their daily travels on electrons as not that many individuals commute over 50km a day, which several PHEVs can do on battery power only.

Consumption testing is consequently based on this assumption, which leads to the overly optimistic “average” fuel usage figures we see on brochures.

A big difference

Some automakers have taken heed of consumer’s complaints and started publishing the fuel consumption for when the battery is not charged up, giving us a more accurate look at how much propellant these vehicles actually use.

Not everyone has been as keen on doing so, but those who have include BMW, Lamborghini, and Mercedes-Benz.

BMW, for example, revealed that its X1 xDrive 30e does 1.1l/100km when the hybrid battery is fully replenished, rising to 6.8l/100km when it’s depleted.

Everyday driving is not as straightforward, however, as it generally includes plenty of stop-start pedaling and unpredictable traffic and weather patterns.

Consequently, there’s significant interplay between the e-motor and petrol engine when driving a PHEV, meaning your real-world consumption in the X1 should sit somewhere between 1.1-6.8l/100km, provided the hybrid battery is charged.

In high-performance plug-ins such as the Lamborghini Revuelto, the PHEV system isn’t so much there for frugality as it is to increase grunt.

As such, you won’t see as big of a benefit on these types of cars, with the V12 Revuelto posting a rather high average of 11.9l/100km with the hybrid battery fully topped up, and only 10km of all-electric range.

The table below shows the fuel consumption of new PHEVs on the market right now, both with their hybrid batteries charged and discharged: