LPG FAQ

Your questions about LPG conversions answered

Is LPG safe?

The danger of an LPG explosion in a car is virtually non-existent. Complete autogas systems, including gas cylinders are subject…

The danger of an LPG explosion in a car is virtually non-existent. Complete autogas systems, including gas cylinders are subject to specialised tests and have to meet extremely high quality standards. As a result, there is no risk of explosion, even during an accident.

AC STAG, the market leader in the LPG system sector (the systems we specialise in), performed a spectacular crash test with vehicles which had LPG systems installed, in cooperation with project partners, independent experts, and in the presence of industry-specific media. The results clearly indicated the absolute safety of the LPG system during an accident.

How long will the gas system last?

The gas cylinder in the system has a validity period of 10 years, although from a technical point of view…

The gas cylinder in the system has a validity period of 10 years, although from a technical point of view it could be used for a much longer duration - its approval for use can be prolonged, but sometimes this is not cost-effective. The high quality electronics should work until the end of car's life, and we give a 5-year warranty for these components.

Reducers and injectors are the parts which wear out. Their lifetime depends on the operating conditions and fuel quality. A good reducer and high quality injectors used on long routes should withstand between 90,000 & 125,000 miles, however when used over short distances in a city, they can become worn out after, for example, 50,000 miles. However, after that time they will have certainly paid for themselves.

Does LPG gas smell?

Yes, in fact a specific odour is added to the LPG to indicate any leaks. This odour is sometimes noticeable…

Yes, in fact a specific odour is added to the LPG to indicate any leaks. This odour is sometimes noticeable behind old worn out cars with simple mixer systems. However, a modern, properly installed gas system must be tight and does not emit any smell.

Does LPG affect performance?

In the modern computer-controlled systems the power loss, if any, is below 5%, which makes it completely unnoticeable to drivers.…

In the modern computer-controlled systems the power loss, if any, is below 5%, which makes it completely unnoticeable to drivers. However the key to full satisfaction are the three following conditions: the system should be carefully selected for a given engine model, make use of high-quality components, at best coming from the same manufacturer, e.g. STAG brand, and be installed in an authorized garage.

Any savings on system components result in losses, not profits. To enjoy dynamic, trouble-free driving it is worth considering the savings from the price difference between LPG and petrol, and not from choosing cheaper components or a cut-price garage.

Does the gas cylinder occupy the car boot?

This is decided by the driver. Obviously, a gas cylinder may be installed inside the car boot and then it…

This is decided by the driver. Obviously, a gas cylinder may be installed inside the car boot and then it occupies some space, but it also offers a large capacity, which means a larger range. However, slightly smaller toroidal tanks are available on the market and these are installed in the place designed for the spare wheel. In this case, the capacity of car boot remains unchanged.

Does LPG affect the engine life?

Certainly no more than petrol or Diesel fuel. The engine is subject to the normal wear and tear, regardless of…

Certainly no more than petrol or Diesel fuel. The engine is subject to the normal wear and tear, regardless of the type of fuel. It is commonly believed that LPG causes valve seat recession, but this also refers to old mixer systems that often have not been properly adjusted (drivers  turned down the LPG dosage to lower its consumption; as a result the engine was running lean and that caused valve seat damage). The modern systems, with a number of sensors and computer control, do not cause any increased engine wear, including valve seat recession.

Can any petrol engine be converted to run on LPG?

Yes. Until recently there was a problem with modern direct injection engines, where petrol injectors were placed in cylinders and…

Yes. Until recently there was a problem with modern direct injection engines, where petrol injectors were placed in cylinders and cooled with injected petrol. This meant that switching off the petrol injection could cause damage to the injectors, so the engine could no longer run on petrol. However, there is already a dedicated system for such engines in which, besides LPG, small petrol doses (so called secondary injections) are also fed to the cylinder for injector cooling at specified time intervals. The only disadvantage of this solution is that both gas and petrol are consumed (it is approximately 2 l/100 km).

Does a gas fuelled car consume more fuel?

Yes, a small amount, because the lower calorific value of LPG creates a consumption per 100 km which is higher…

Yes, a small amount, because the lower calorific value of LPG creates a  consumption per 100 km which is higher than that of petrol (by 10 to 20% depending of system). However, due to significantly lower prices, driving on LPG is much more cheaper than on petrol.

What is the fuel consumption of LPG engine?

Car fuels, including LPG is sold in litres and measuring in litres, a car consumes more gas than petrol to…

Car fuels, including LPG is sold in litres and measuring in litres, a car consumes more gas than petrol to travel the same distance at the same speed. The differences is 20 to 30% to the detriment of autogas.

However, for the price of 1 litre of petrol we can buy about 2 litres of autogas, so despite the difference in consumption, driving on LPG in favourable conditions gives savings of 40-50%.

Does a gas-fuelled car also consume petrol?

The engine may also use petrol for so called secondary injection. The secondary injection of petrol occurs when the gas…

The engine may also use petrol for so called secondary injection. The secondary injection of petrol occurs when the gas and petrol feeding systems work simultaneously, e.g. 90% gas and 10% petrol  in some rpm ranges. The use of two fuels simultaneously is unnoticeable to drivers and protects the engine in a situation where the system cannot meet the fuel demand of the engine.

 In indirect injection engines, the secondary injection of petrol is only programmed in some cars, while for direct injection engines it is necessary in order to ensure the correct functioning of the engine running on gas and to protect petrol injectors.

The exception is the direct gas injection system. In direct petrol injection engines, a situation may occur, e.g. at low rpm, when the engine uses only petrol, but on average the car uses much more gas than petrol. It all depends of the type and class of the and class and the engine type.

Is LPG system installation in an older, large mileage car safe?

If the engine is in good operating order there should not be any problem with system installation. However, it should…

If the engine is in good operating order there should not be any problem with system installation. However, it should be noted that an small defects in the fuel feeding system that could create small problems for petrol, may be clearly visible for gas feeding. Therefore, in older cars, it is worth replacing the spark plugs and HV cables when installing the LPG system.  If the engine has no hydraulic lash adjuster it is necessary to perform valve adjustment.

A problem may arise with the engine harness at the installation stage: in older cars the electrical system does not react well to dismantling for any reason, and in some very old models it may disintegrate into pieces. If so, any worn components should be replaced or repaired, which is not a problem, but can cause an increase in installation cost.

Must the car undergo a special inspection before LPG system installation?

For late model cars it is not necessary. Any car, regardless of type of fuelling should be subject to standard…

For late model cars it is not necessary. Any car, regardless of type of fuelling should be subject to standard inspections and oil replacements according to the maintenance intervals adopted by the owner or suggested by the manufacturer.

However, older cars should be inspected. The engine operating condition is very important, e.g. excessive gas purge to the crankcase due to the wear of piston rings or cylinders is unacceptable. The engine should not consume too much oil. 

Before installing a LPG system it is necessary to ensure that the engine ignition system is in perfect condition because gas ignition places a greater demand on the ignition system than the petrol ignition.