The R1,900 difference between filling your car with petrol vs gas

South African motorists willing to convert their cars to run on Liquefied Petroleum Gas (LP Autogas) could save R1,877.63 per month by refuelling with the petrol alternative instead.

LP Autogas, or LPG, comprises hydrocarbon compounds like petrol and diesel, but its main components are propane and butane.

These are released when extracting oil and natural gas and refining crude oil, so compressing them converts them to a liquid state and creates LPG, which is cleaner and cheaper than petrol and diesel

That said, those motorists looking to benefit from the alternative fuel will need to convert their car to run on LPG – which requires significant investment.

Another consideration is that a litre of gas has less chemical energy than a litre of liquid, meaning an engine needs more fuel to produce similar power.

A converted vehicle will see increased fuel consumption of 15% to 25% on LPG compared to petrol. For example, a car consuming 7.5l/100km on petrol will typically consume 8.8 to 9.4l/100km on LPG.

Despite this higher average fuel consumption, LP Autogas delivers substantial savings, especially for South African motorists, due to the country’s various fuel taxes.

Retail petrol prices in South Africa carry substantial levies, including the General Fuel Levy (GFL), Road Accident Fund (RAF) levy, and customs and excise surcharges.

Autogas is exempt from several of these transport-specific fuel surcharges, making it significantly cheaper per litre at the pump.

As a result, LP Autogas typically sells for 30% to 40% less per litre than retail petrol, but thanks to current sky-high petrol and diesel prices, that is closer to 50%.

Factoring in the 20% higher volumetric fuel burn, the net cost per kilometre driven on LPG is 20% and 30% less than on petrol, representing substantial savings for local motorists.

Below is a breakdown of inland petrol vs LP Autogas prices in South Africa over the past six months, provided by local automotive fuel conversion solutions provider, Isinkwe Energies:

Saving over R20,000 per year

The average passenger car LP Autogas tank has a gross capacity of 45 to 65 litres, though the exact size depends on the tank geometry and the car’s available space.

The standard “doughnut” shaped tanks are installed in the spare-wheel well beneath the boot floor and have a gross capacity of between 40 and 60 litres.

Larger cylindrical tanks can also be mounted against the back of the rear seats in the boot or along the chassis rails of bakkies or other light commercial vehicles, and offer expanded capacity up to 90 litres.

International safety regulations also require LPG tanks to be fitted with an automatic Overfill Prevention Device (OPD) that stops filling at 80% capacity.

Below is a breakdown of how this affects LPG car fuel capacity:

Considering this, the average South African motorist driving 1,500km per month on LP Autogas can expect to refuel two to three times a month depending on their vehicle and tank choice.

A motorist driving a petrol vehicle consuming 7.5l/100km over 1,500km per month uses 112.5 litres of Unleaded 95. At an inland price of R30.25 per litre, this results in a monthly fuel bill of R3,403.13.

Switching to LP Autogas increases fuel consumption by 20% to 9.0l/100km, requiring 135 litres of gas to cover the same distance.

However, at R11.30 per litre, monthly LPG spend drops to R1,525.50 – an immediate monthly saving of R1,877.63.

Below is a breakdown of what these savings figures look like over 12 months, provided petrol and LPG prices remain unchanged:

Depending on what type of LPG conversion a motorist opts for, the more than R20,000 cost savings could cover the cost of conversion within 12 months.