How much petrol you waste sitting in your car with the engine running

Motorists can burn through roughly R53 worth of petrol every hour the engine is running, even if they aren’t moving.

News headlines over the past two weeks have been dominated by the latest updates regarding South Africa’s petrol and diesel prices, which are expected to increase dramatically this April.

The country’s fuel prices are adjusted on the first Wednesday of every month, based on the fluctuating price of oil and the US dollar/rand exchange rate.

The international Brent Crude oil price has skyrocketed since the start of March, when the United States and Israel launched coordinated attacks against Iran and eliminating its Supreme Leader.

Iran retaliated by attacking the US and its allies across the Middle East, disrupting oil production across the region while also closing the crucial Strait of Hormuz shipping lane.

Consequently, oil prices have surged more than 40% this month to over $100 per barrel.

In South Africa, the Central Energy Fund’s latest data indicated that petrol prices will increase by around R4 per litre, while diesel is facing an even larger shock of R7 per litre.

Naturally, this means it’s more important than ever for motorists to reduce their fuel consumption, as bad habits can easily rack up hundreds of rands in wasted petrol.

One of the ways drivers can do this is by minimizing the amount of time the engine is idle, as cars still use fuel even when they aren’t moving.

How much fuel is wasted in an idle car

According to the South African vehicle tracking firm CarTrack, most passenger cars and commercial vehicles can burn through multiple litres of fuel every hour while idling.

This is because internal combustion engines still need to burn fuel even when there is no throttle input to maintain a minimum rev count and prevent the engine from stalling.

“Idling is when a driver leaves the vehicle engine running when the vehicle is parked. Every day millions of cars and trucks idle unnecessarily, which can have many implications,” said CarTrack.

“This could be in stop-and-go traffic, drive-through lines, or loading docks. As well as running the vehicle to power heating, air conditioning, and electronic devices.”

CarTrack noted that the average idling passenger car consumes between 0.7 and 2.65 litres of petrol per hour, while diesel trucks can use as much 4 litres per hour.

Petrol 95 is currently retailing for R20.30 per litre at inland rates as of March 2026, while the wholesale price of diesel 0.005% is pegged at R18.60 per litre.

This means motorists sitting in their car with the engine on spending anywhere from R14.21 to R53,795 in wasted petrol, while diesel trucks are burning through R74.4 every hour.

If the Central Energy Fund’s predictions hold true and petrol and diesel prices increase to R24.57 and R25.75 per litre in April, idle motorists will be spending between R65.11 and R103 on unused fuel every hour.

Cartrack explained that idling the engine for more than 10 seconds wastes fuel and produces more carbon emissions than turning the engine off and restarting it later.

Additionally, idling an engine results in more wear and tear on the components as there is less oil to lubricate the motor, causing friction.

Partially combusted fuel can also damage the engine, spark plugs, and exhaust system, leading to costly repairs down the line.

It’s therefore important to avoid letting the engine run whenever possible, even if you think you won’t be idle for very long.

This includes everyday situations, like sitting in the car with the AC and radio on while waiting to pick up your kids from school, or driving in congestion.

Creeping along in bumper-to-bumper traffic is not an efficient use of fuel, so it is recommended that motorists find alternate routes or leave at different times to avoid traffic as much as possible.