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LPG vs CNG: Autogas Conversion Basics for South Africa

15 Jul 2026 Ethan Lowery
LovatoautogasLPGCNGconversionbuying guide

An autogas conversion lets a petrol engine run on gas instead of petrol, and there are two gases to choose from: LPG and CNG. Both are fitted as a bi-fuel system, so the vehicle keeps its petrol tank and injection and gains a second gas fuel system alongside it. The engine starts on petrol, warms up, and the changeover switch moves it to gas for normal running. What differs between LPG and CNG is the fuel itself, how it is stored on the vehicle, and where you can refill it. That difference decides which one is right for your vehicle and your routes.

This note covers how the two fuels compare, what a modern sequential system does with each, and how to choose between them in a South African context.

What LPG and CNG actually are

LPG (liquefied petroleum gas) is a propane and butane mix, the same family of gas sold for domestic and industrial use. It stores as a liquid under modest pressure, in the region of 8 to 10 bar, so an LPG tank is a moderate-pressure vessel that fits in the boot as a cylinder or as a toroidal tank in the spare-wheel well. Because it is liquid in the tank, LPG carries a lot of energy in a small volume.

CNG (compressed natural gas) is mostly methane, the same gas piped for heating and cooking. It does not liquefy at normal temperatures, so it is stored as a compressed gas at high pressure, around 200 bar (20 MPa). That means a CNG tank is a heavy high-pressure cylinder, steel or composite, and the system needs a high-pressure regulator to bring that 200 bar down to a working pressure the engine can use. CNG holds less energy per litre of tank space than LPG, so a CNG tank of the same size gives less range.

How a sequential system handles each fuel

A modern conversion is a sequential injection system: gas is injected in timed pulses at each intake port, one gas injector per cylinder, under the control of a gas ECU. The Lovato injection kit, the ECU, the gas injectors and the changeover switch are largely common between LPG and CNG. The part that changes is the reducer.

  • On LPG the reducer is a vaporiser. It drops the tank pressure and turns the liquid LPG into vapour, using heat from the engine coolant to do the vaporising. That is why an LPG reducer plumbs into the cooling system.
  • On CNG the reducer is a high-pressure regulator. The gas is already vapour, so the reducer’s job is to step 200 bar down to the working pressure the gas rail needs, in stages, again warmed by coolant to offset the cooling that comes with a large pressure drop.

Everything downstream of the reducer, the gas rail, the injectors, the pressure and temperature sensors and the ECU that doses the gas, works on the same principle for both fuels. The engine still runs its normal petrol strategy underneath, and the gas ECU emulates the petrol injectors while gas is selected so the petrol ECU sees no fault.

Fuel availability and cost in South Africa

This is usually the deciding factor. LPG is widely available in South Africa because it is already distributed for domestic and commercial use, so sourcing and refilling LPG is far easier across most of the country. CNG refuelling is limited to a small number of stations, concentrated in parts of Gauteng, so a CNG vehicle only makes sense if your routes pass a station that can fill it. Confirm what is actually available on the roads you drive before you commit to CNG.

On running cost, both gases are cheaper per kilometre than petrol, which is the whole point of converting. Gas has a lower energy density than petrol, so you use a little more of it by volume, but the price gap still leaves a saving. The saving has to pay back the cost of the conversion over the kilometres you drive, so a high-mileage vehicle pays back a conversion far faster than one that sits.

Which one suits your vehicle

Match the choice to three things: fuel availability on your routes, the space you have for a tank, and how you drive.

  • If you want the widest refuelling network and a straightforward boot or spare-well tank, LPG is the practical choice for most South African vehicles.
  • If your routes reliably pass a CNG station and you want the cleanest burn, CNG is viable, but plan the tank weight and range around the high-pressure cylinder.
  • Confirm the engine is a port-injection petrol engine suited to a conventional sequential kit. Direct-injection engines need a different approach, so flag the exact engine before ordering.

How to order or request a quote

Tell us the vehicle, the engine and injection type, the fuel you want to run and the tank space you have, and we will confirm the matching Lovato conversion kit, reducer and tank, with the lead time. Order genuine Lovato components by part number on Omnipart.