LPG vs. Petrol

Untitled-2While the price of petrol is currently low, compared to what it has been for the past few years, some observers say it must go up again eventually.  If it does, you may want to think about  converting your car to LPG.

The Federal Government rebate is no longer available and, due to the complexity of modern engines, the conversion cost has increased, so make sure you get a firm quote from an LPG installer before proceeding. Your pay-back period will depend on your vehicle and how far you drive each year.

But have you got all the facts?

Environmental impact

The environment wins if you make the change, leading to lower greenhouse emissions. The Australian Government has calculated that the mass of CO2 (greenhouse) gas released from the exhaust pipe by the burning of one litre of fuel is:

  • 2.3 kg for Petrol
  • 1.5 kg for LPG.

LPG = Fewer kilometres per litre

You can expect a 15-30 per cent increase in fuel consumption over petrol per kilometre because the lower energy content of gas requires more to be burned in the engine compared with petrol and you have to factor this into your calculations.

In knowing all this, is a change to LPG worth it?

You have to be sure all the figures add up and that you are going to be better off economically if you convert. Another option is to buy a second hand car that was manufactured with LPG fitted, such as the Ford Falcon LPi models. These are LPG-only (ie, no petrol system is fitted at all). They are no longer available new but were produced for several years up to 2014, so there are a good number of low kilometre examples available on the market at reasonable prices. The Holden Commodore was also offered for a couple of years with a factory-warranted LPG system.

You can keep up to date with daily fuel prices by monitoring NRMA’s fuel pages. Thinking about purchasing a LPG vehicle? NRMA Car Loans offer great rates to NRMA Members.

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Fuels – which should you use?

Motorists can be forgiven for being confused about the fuels available and what their car needs.  There are five types of petrol now available (standard unleaded, 95 premium, 98 ultra premium, E10 and E85) as well as Diesel and LPG.

This blog is to help clear up the confusion about which fuels are the best to use. We begin with premium unleaded.

Premium Fuels – is there a benefit?

Petrol vehicles are designed for a specific octane fuel and normally do not benefit from using higher octane fuel.

If the manual says you can use more than one type of petrol or blend, you may get the advantage of reduced fuel consumption (but only if your vehicle’s engine automatically adjusts its parameters to take advantage of higher octane).  Conversely, you may be able to save money by using a lower octane fuel, if the manufacturer states the vehicle will run normally on it.

As a rule of thumb:

  • 95 premium can give around 4% lower fuel consumption than 91, assuming the engine computer adjusts to take advantage of the octane difference.
  • 98 might give 3% reduction over 95, again assuming the computer adjusts the engine parameters.

The overriding recommendation is to consult the owner’s manual for your vehicle and use fuel of the octane listed.  Some motorists report lower fuel consumption using higher octane fuel.  If you wish to check this for yourself, be sure to record your fuel consumption for at least 10 tanks before you make the change, so you have a good baseline.

Try and check your baseline under normal conditions – if you have an unusual country trip in the middle of your test period, for instance, it will result in atypical figures.

Conversely, if your driving is normally on highways, a week of city driving will bias your figures.  Then change to the higher octane fuel and do a check for the next 10 tank fills and compare the figures.  If the savings from any reduced fuel consumption are outweighed by the extra cost of the premium fuel, it is obviously not economically sensible to use the higher octane.

In our next blog, we’ll look at ethanol in petrol (E85 and E10).

Which premium unleaded fuel do you find the most efficient and cost effective?

Ethanol in petrol
Diesel – fuel for thought

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Ethanol in petrol

Dollarphotoclub_31429154Ethanol has been widely available now for around 10 years, being sold as E10. It is a colourless alcohol, the same as in alcoholic drinks and is manufactured from grain or sugar.

The CSIRO has calculated that an E10 blend cuts overall greenhouse emissions by around 3 per cent. However it’s more costly than petrol to produce and requires special storage facilities.

Testing shows that fuel consumption can increase by 3-4 per cent when using an E10 blend in vehicles that do not have the capability to take advantage of E10’s higher octane, in which case the fuel consumption impact is small. 10 per cent ethanol mixed with petrol should not affect the majority of vehicles on our roads.

The motor industry’s website advises which cars can use E10, E5 or no ethanol at all.

Ethanol is currently rebated at the normal fuel excise, so E10 should be marginally cheaper than standard unleaded petrol at the bowser.

What’s your experience with E10? Is your car cheaper to run overall and has E10 had any effect – good or not so good – on your car’s performance or reliability?

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Using Premium Unleaded Petrol

Unleaded Petrol Pump

Which petrol is best for your vehicle?

Have you ever used Premium Unleaded petrol in your vehicle instead of Regular Unleaded? Did it seem to go further, dollar for dollar? Did it have any noticeable effect at all?

If your car is optimised to run on Regular Unleaded 91 RON (Research Octane Number), then using PULP may have a marginal effect on the fuel consumption and cost saving.

So if, hypothetically, a vehicle was designed to operate on any octane (which is never the case), using 98 RON would give a seven per cent increase in power or a seven per cent decrease in fuel consumption compared with using 91 RON. Cars that are designed to run on PULP 98 RON may still run on 95 RON but you may lose around three per cent of power, or increase fuel consumption by this amount.

Therefore, if ultra premium fuel costs more than seven per cent more than 91 RON, is it economically unwise to use it?

The simplest advice is to use the octane recommended in your owner’s manual.

Have you used Premium Unleaded and noticed any improvements in your vehicle’s fuel economy or performance?

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Which grade of diesel should you use at the bowser?

Considering today’s ever improving diesel engines, our Members have been asking which grade of diesel should they choose at the pump.


DECISIONS, DECISIONS: Pricing is not the only thing you need to consider when filling up at the bowser.

NRMA Motoring Advice recommends the Low Sulphur grade Premium Diesel option, as this is the only type of fuel that is compatible with today’s diesel fuel systems. 

In older vehicles, the usage of  regular diesel can cause significant sulphuric acid build up which quickly corrodes piston rings, cylinder linings, valves and cylinder head. Oil changes are also required frequently, doubling the vehicle’s manufacturer recommendations.

For newer vehicles, high pressure diesel direct-injection systems such as common rail diesel engines are highly sensitive to high sulphur fuels. Also, electronic metering systems are rendered inaccurate by deteriorating fuel injector pins.

Overall, high sulfur fuels increase vehicle repair and maintenance costs are for both vehicle types. Low sulphur diesel can be used in any vehicle or stationary diesel engine that currently runs on regular diesel.

Low sulphur diesel summary:

  • Reduces sulphur in fuel potentially reduces the risk of corrosive wear in the engine;
  • Reduces the sulphur content does not inhibit engine performance; and
  • Reduces sulphur facilitates the introduction of new diesel exhaust treatment catalyst which will further enhance the reduction of environmentally sensitive diesel emissions;
  • Reduces the ultra fine particles from diesel engine exhausts will improve local air quality;
  • Reduces sulphur dioxide emissions, which contribute to acid rain, will reduce the risk of acid rain occurring.

Are you a regular user of low sulphur diesel? Have you noticed any improvements to your vehicle’s running and repair costs?

Have any more questions that you would like us to answer? Our Motoring Advice Team are available to provide advice and information on just about anything motoring related for NRMA Members. You can reach the team on 13 11 22 (Mon-Fri 9am-5pm)

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