E85 v E10 v premium unleaded

[vztrt]

I guess you could see the article as a bit of a Holden add but E85 seems to get a drubbing from a financial point of view.
I would have liked to see LPG put in the mix to compare costs as it seems to be more of a cheaper motoring story.

http://theage.drive.com.au/motor-new...205-1ahgx.html

Ethanol put to the test: E85 v E10 v premium unleaded
Stephen Ottley and Toby Hagon
February 5, 2011

Ethanol is greener but it may not lead to cheaper motoring, report Stephen Ottley and Toby Hagon.

The race is on to replace oil with greener forms of fuel. As the world grows increasingly concerned by our declining oil supplies, car makers are trying to find the best replacement - or the one that will be most accepted.

Some are convinced electrification is the answer. Others believe hydrogen will be the best outcome. And there are those who believe the solution can be found in sugar cane fields, or even at the tip.

Much debate surrounds the best zero-emissions fuel to employ in the long term but biofuels - those produced from biological materials - are also receiving their fair share of attention.
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Ethanol started off as the bad boy of alternative fuels, damaging some fuel systems not designed to take what is almost pure alcohol - albeit with additives to make people vomit if they drink it and blended with petrol in varying ratios.

It's quickly becoming more popular as a way to use existing infrastructure but produce fuel locally, reducing transport costs - and emissions. Even taking into account energy used in production and transport, ethanol is claimed to significantly reduce CO2 emissions because it uses materials that absorb CO2 during the growing process.

The more immediate benefits of ethanol are also obvious: it is available now, it can be easily phased in at service stations, it can be sourced from waste products and it has a higher octane rating, which means more power. Already some enthusiasts are modifying their cars to run on E85 - a blend of petrol and up to 85 per cent ethanol - to take advantage of the increased performance.

While almost all new cars and most used ones can use a blend of 10 per cent ethanol and 90 per cent petrol (known as E10), higher blends are available in countries such as Brazil, which has reduced its dependence on imported oil and instead produces the majority of its own fuel locally.

In a classic chicken-and-egg dilemma, car makers and fuel companies have been at a stalemate about using the fuel in Australia. Fuel companies haven't rushed E85 to market, given only a handful of cars are engineered to take it, while car makers argue there's no point selling E85-compatible cars because you can't buy the fuel.

Last year, though, Holden bit the bullet by modifying two of the three engine variants available in its top-selling Commodore range to run on E85. However, Holden wasn't the first to use E5. Saab, Chrysler, Dodge and even Bentley offer E85-compatible vehicles.

It formed a consortium with various companies, including biofuel company Coskata and Caltex, to develop ethanol from common household waste (see breakout). Caltex also committed to rolling out a network of "Bio E-Flex" pumps. So far about 30 are pumping E85 - as well as a handful of independent stations - with plans for a network of 100.

But all is not rosy with E85. Because it has less energy per litre than petrol, you'll use more of it - car makers say about 30 per cent more. That means the price has to be about one-third less than regular petrol to make it economically viable.

Then again, that's not taking into account the claimed environmental benefits, which Holden hopes will tempt some to switch to E85.

Claims are one thing. How it really performs is another. Drive put E85 to the test in the real world. Taking into account convenience, the effect on the hip pocket and performance, we assembled three identical Holden Commodore Omega sedans fitted with E85 compatible 3.0-litre V6 engines.

The cars arrived with near-empty tanks and we quickly ran them down as low as possible before filling them each with a different brew. One car ran exclusively on E85, the second on E10 (a fuel mandated for use in NSW and becoming increasingly popular in Victoria) and the final car used the most expensive 98-octane premium unleaded - claimed to increase driving range, produce more power in some cars and better clean engines.

At a Caltex service station near Sydney airport, the trip computers were reset, tyre pressures checked and the cars hit the road.

The trio was driven in convoy (leaving adequate space in between each vehicle to negate the potential fuel savings of drafting the car in front) with a team of drivers rotating between the cars to cancel out any particular driving style influencing the result.

Country roads

The first stage of our test was the 877-kilometre freeway run from Sydney to Melbourne - and back again. The idea was to sit the cars on the 110km/h speed limit that dominates the dual carriageway run between Australia's two most populated cities.

Holden claims the Commodore can travel from Sydney to Melbourne on a single 73-litre tank of regular fuel - something we've verified previously - but the big test is whether it can match the feat running on E85, which contains less energy per litre. Holden estimates you'll use between 25 per cent and 40 per cent more fuel when using E85.

CO2

That didn't bode well for a stop-free run to Melbourne. Nor did it look likely that we would achieve the 20 per cent to 40 per cent reduction in CO2 emissions that ethanol supporters claim is possible. (The actual claim depends on how far the fuel is transported from production site to bowser - transporting it from Queensland to Victoria, for example, will result in more transport emissions.)

Just as when you're running on regular petrol or premium unleaded, the Commodore's 3.0-litre V6 engine feels strong and the E85-fuelled car provides no perceptible difference to either engine sound or responsiveness.

While drivers weren't told what fuel was in each car, we were only a few hundred kilometres south of Sydney when it became obvious. The driving range predicted by the Commodores' on-board trip computers started to space out significantly. The E85-fuelled car was pessimistically suggesting on its trip computer that 500 kilometres or so would see the tank dry, although it continued to recalculate and effectively extend the range.

The trip computer on the car running with premium unleaded was predicting it would comfortably reach Melbourne, indicating a total range of more than 900 kilometres.

The car running E10 was not as optimistic but still predicted it could make Melbourne's outskirts.

Theoretically, if you refuelled on the outskirts of Sydney, the E85 car still wouldn't be able to reach the outskirts of Melbourne - at least, not when the car is driven normally and with the airconditioning operational, as ours cars were.

There is E85 available in Canberra but the thought of a 120-kilometre detour isn't desirable for those looking to do their bit for the environment.

Still, even if it falls short, the Commodore can be fuelled on any blend of petrol; its electronics are smart enough to cope with any mix of petrol and E85, adjusting the engine tune accordingly. For the integrity of our test, we didn't want to alter what was in the tanks, so the solution was to carry an additional 40 litres of E85 - just in case.

It was a prudent move, with the E85 car needing to be topped up with an extra 40 litres (from jerry cans) along the way, something that was added to our fuel use figures once the calculators were brought out.

fuel use

Fuel use on the freeway for the E85-fuelled car averaged out at 9.6 litres per 100 kilometres. That's 21.5 per cent more than the most frugal of our trio, which was - predictably - the car fuelled with premium unleaded (7.9L/100km). The E10 car was sandwiched in between, using 8.2L/100km.

However, it was the E10-fuelled car that was the cheapest to run over the entire 1764-kilometre, two-day highway trip. It used $172.65 in E10, compared with $189.15 worth of 98 RON for the car running on premium unleaded.

Somewhat surprisingly, the E85-fuelled vehicle cost the most at $194.68.

fuel costs

On average we paid just 107.3¢ a litre for E85, compared with 121.3¢ for E10 and 137.7¢ for premium unleaded. Caltex has committed to maintaining a 20¢-a-litre price difference between E85 and regular unleaded (the gap to E10 is likely to be less).

However, it's the percentage difference that counts and vagaries in pricing could easily change the equation (see breakout for more on ethanol pricing).

During the freeway test, we managed a brief diversion to conduct a simple acceleration test using satellite-based timing equipment to determine whether there were any differences in the three fuels' power outputs.

There were but our track tester admitted feeling little performance difference between the E85 and E10 cars.

To be fair, Holden admits the outright power of the Commodore doesn't really change when running on E85 but there are claimed benefits to torque, or mid-range pulling power, which should mean you don't have to push the accelerator as far to achieve the desired result.

Still, the E85-fuelled car proved 0.3 seconds quicker in the sprint to100km/h compared with the E10 Commodore. As expected, the car running premium unleaded was quicker again (by 0.3 seconds), suggesting it's the fuel of choice if performance is your goal.

City streets

After our freeway run, it was time to drive the cars in the conditions in which most drivers spend the majority of their time - negotiating city streets, stop-start traffic and major arterials.

Our test began at the same Caltex service station in inner south-west Sydney. Two test routes were chosen to give a good representation of city streets. In total, the cars would travel almost 300 kilometres, taking into account school zones, peak-hour traffic and the usual snarls that can slow city motoring. The average speed was a fraction less than 30km/h.

Again the Commodores were primed in the same way with the three different fuels. And, again, it was the car running on premium unleaded that suggested it would go furthest between refills, using a respectable 11.7L/100km.

The E10 car used 8.5 per cent more, while the E85 car used a substantial 2o per cent more fuel (39 per cent more than the premium unleaded car) and more than 30 per cent more in some situations. While some have claimed E85 works better on a freeway, our results suggest the fuel-use ratios are similar whether on a freeway or in the city. Again it was the E10 car that was the most affordable to fill, although extrapolating out over 15,000 kilometres of annual city driving, the savings would be in the order of $100.

If petrol prices rose dramatically and the cost of ethanol (or E85) was lower, the benefits could swing the other way. Petrol at $2 a litre, for example, with E85 at $1.50 a litre, would swing the cost advantage in favour of E85. Indeed, any time when E85 was at least 25 per cent less than E10, it would be more affordable to run on E85.

graph2a

graph 2b

Which is best?

There is no clear-cut call on which fuel is best. Each gives different benefits, depending on what you're trying to achieve. If you don't like visiting petrol stations and appreciate the performance benefits (and extra additives claimed to keep engines cleaner) in premium unleaded, then it's the fuel of choice.

Even around town, a tank of premium unleaded should eke another 30 kilometres out of a tank (compared with E10). And you have a (slightly) better chance of winning the traffic-light grand prix.

If you're trying to reduce your fuel bills, though, E10 is the best of the three fuels tested here. During an average year of driving - assuming about 15,000 kilometres and at today's fuel prices - you should save about $100 over E85 or premium unleaded. That's assuming your car is formulated to use E10.

And remember that in previous Drive tests, we established that E10 was more expensive to use than regular unleaded, which is being phased out in NSW to meet a government mandate.

Finally there's E85, the new cocktail that - to be fair - is hailed an environmental hero and not a budgetary one. Assuming the CO2 calculations are correct - there's debate about exactly how much CO2 is saved using ethanol - then running the new Commodore on E85 should reduce greenhouse emissions.

It's difficult to say exactly, because the claimed CO2 benefits of E85 vary depending on where the fuel is being used and how it is produced but the E85 Commodore emitted somewhere between 5.5 per cent and 26 per cent less CO2 than the E10 car. The difference was greater again compared with the premium unleaded car.

But running the new Commodore on E85 comes at an additional financial cost - at least for now (see breakout). The E85 car was the most expensive to fuel on our test (remembering fuel prices can vary markedly), even if only just. Some will no doubt see it as a small price to pay for potential environmental benefits.

There's also the less easily measured benefit of creating local jobs and reducing our dependence on imported fuels, something that comes to the fore when price volatility kicks in due to tensions in the Middle East.

Whichever way fuel prices go, though, they're unlikely to remain where they are and having the ability to choose what fuel to use has to be a good thing.

For more on environmentally friendly fuels, go to drive.com.au/green-cars

Run on recycled rubbish

rubbish

An estimated $400 million investment in a revolutionary ethanol plant in Melbourne will provide up to 200 million litres of the biofuel from household rubbish — but it's at least a few years away.

While Australian ethanol is produced in Queensland and NSW from waste products of wheat and sugar production, US-based ethanol producer Coskata has developed a new process of extracting more ethanol from biomass and even household waste.

While traditional ethanol production yields up to 100 litres from a tonne of feedstock, the Coskata system can yield between 320 litres and 400 litres a tonne by using proprietary micro-organisms and a patented process.

The end result is the same thing — pure alcohol, which is then blended with petrol, typically as E10 (10 per cent ethanol, 90 per cent petrol) or E85 (between 70 per cent and 85 per cent ethanol and the remainder petrol).

Holden's ethanol push — part of a partnership with Caltex, Coskata, Mitsui, Veolia and the Victorian government — is planned to help reduce Australia's dependence on fossil fuels by about 30 per cent, though Coskata believes ethanol could account for "as much as 50 per cent of global transport fuel".

For all its benefits, there are some major drawbacks to ethanol and the biggest one is that many older cars won't run on it, even the milder E10 blend. The NSW government is mandating the use of E10, so modern vehicles are generally OK. Check the fuel filler flap or owner's manual for your car.

As for E85, only cars specifically developed for it are able to use it (check the filler flap), otherwise you risk damaging the fuel system.

The price you pay

E10

Its production may have nothing to do with the distillation of crude oil but the price of ethanol — the core component of E85 — will be naturally linked to the pump price of petrol and diesel.

Just as LPG, diesel and petrol prices rise simultaneously (despite much of Australia's LPG being sourced locally) the price of ethanol is expected to follow more traditional fuels up — or down.

"There is a definite correlation between the price you get for your ethanol and the price of petrol," says Wes Bolsen, the chief marketing officer and vice president of US-based biofuel company Coskata, which is providing the technology for a new ethanol plant in Victoria.

While the cost of producing ethanol is unlikely to rise dramatically with that of oil — except for some transport costs — the price volatility comes down to supply and demand.

But Bolsen says the natural market dynamics will be a win for consumers and the environment, with ethanol claimed to reduce CO2 emissions by up to 40 per cent (depending on where the fuel is sourced).

He says there will naturally be winners out of the increase in demand for ethanol but because of its local production, it means keeping more money in Australia.

"What is good for the environment and economic growth is also good for someone's pocket," Bolsen says. "It is my job to make the fuel as cheap as possible."

He also admits that the emerging Australian ethanol industry will benefit from a rise in fuel prices.

"It's a great thing for us [those in the ethanol production industry] for gas prices to go up," Bolsen says. "More people go and build facilities so it brings down the cost again."

The energy and environment director of Holden, Richard Marshall, admits ethanol is not the silver bullet but more a way to deliver choice and potentially future-proof motorists.

"So today with the price of E85 being where it is, depending on the fuel cycle and the price swings you get on [unleaded petrol], depending on when in that cycle you fill up, you may find it cheaper to run on E85 or it may be more expensive to run on E85," he says. "That's where it comes back to consumers making that choice when they fill up."

Unexpected factors can also influence the price of ethanol and petrol and the relationship between them. The brewing conflict in Egypt has increased oil price volatility, while recent floods in Queensland and this week's cyclone will have impacted on ethanol supply.

[Carby]

Don't know why Holden are going down this route - the E85 fuel is pretty inefficient and costs more to run - will people use it to help save the planet? Not in my opinion.


A dedicated LPG system is coming later in the year but I'm buggered why they haven't gone down the diesel route for the Commodore (and Falcon) - one would think it they would be ideal for heavy vehicle's like those two.

[prasac]

Originally Posted by Carby

Don't know why Holden are going down this route - the E85 fuel is pretty inefficient and costs more to run - will people use it to help save the planet? Not in my opinion.


A dedicated LPG system is coming later in the year but I'm buggered why they haven't gone down the diesel route for the Commodore (and Falcon) - one would think it they would be ideal for heavy vehicle's like those two.

more than likely to make the engines Euro compliant. they don't have the money/time to design a whole new engine, making the car flex fuel allows them to omit lower emissions.

what i heard though im not sure if it's true, someone can correct me if im wrong they do an average on the engine, so if 76 or under is a passing grade. and it scores a 100 on 98RON and a 50 on E85, the average is 75, so officially it passes.

[Jason[98.EL]]

I agree I think a diesel variant of the falcon would be a big seller

I guess that it is up to ford au so we might not see it ever

[jpd80]

Fuel use on the freeway for the E85-fuelled car averaged out at 9.6 litres per 100 kilometres. That's 21.5 per cent more than the most frugal of our trio, which was - predictably - the car fuelled with premium unleaded (7.9L/100km). The E10 car was sandwiched in between, using 8.2L/100km.

However, it was the E10-fuelled car that was the cheapest to run over the entire 1764-kilometre, two-day highway trip. It used $172.65 in E10, compared with $189.15 worth of 98 RON for the car running on premium unleaded.

Somewhat surprisingly, the E85-fuelled vehicle cost the most at $194.68.

I can't help thinking that the trip would have been even cheaper had they just stuck
good old 91 ULP in the tank. More zing than E10 and about the same price...

[JC807]

e85 needs huge compression or forced induction and tuned to suit to make any real benefits.

and it should still be 99 cents a litre, not the $1.17 i've seen Caltex sell it for - what a joke.

still i think Caltex getting the ball rolling by selling it can only be a good thing for the future of performance turbo cars in this country.

[phillyc]

Originally Posted by JC807

e85 needs huge compression or forced induction and tuned to suit to make any real benefits.

and it should still be 99 cents a litre, not the $1.17 i've seen Caltex sell it for - what a joke.

still i think Caltex getting the ball rolling by selling it can only be a good thing for the future of performance turbo cars in this country.

Ethanol has zero excise. This will rise to 25cpl as July 2011. However, domestic producers will receive an offset of 22.5cpl and reducing by 2.5cpl for 5 years. Then no offset.

Petrol has 38.1cpl excise. IMO there should be about 30cpl difference.

Originally Posted by GoAuto

The Biofuels Association of Australia (BAA) said that although the ethanol excise provided certainty for local biofuel producers it did not give them enough time to compete on a level playing field with biofuel importers. Currently, 52 per cent of Australia's petrol and diesel fuel is imported, generating a trade deficit of some $17 billion

That is as good a reason as any to substitute petrol with ethanol.

[irish2]

Originally Posted by Carby

Don't know why Holden are going down this route - the E85 fuel is pretty inefficient and costs more to run - will people use it to help save the planet? Not in my opinion.


A dedicated LPG system is coming later in the year but I'm buggered why they haven't gone down the diesel route for the Commodore (and Falcon) - one would think it they would be ideal for heavy vehicle's like those two.

The one benefit of E85 is it isn't made totally from oil. LPG is.

[JC807]

Originally Posted by phillyc

Ethanol has zero excise. This will rise to 25cpl as July 2011. However, domestic producers will receive an offset of 22.5cpl and reducing by 2.5cpl for 5 years. Then no offset.

Petrol has 38.1cpl excise. IMO there should be about 30cpl difference.

That is as good a reason as any to substitute petrol with ethanol.

IMHO ethanol produced in this country by Australian companies using Australian byproducts and waste should never be pegged (albeit lower total price) to petrol prices. ethanol and petrol are vastly different products (local and global) and the price of one shouldn't affect the price of the other, except the 15% of the E85 fuel which is still petrol.

(its kinda like iTunes australia charging $2.19 per track simply because CDs are more expensive here than the USA (official iTunes response to my complaint, nevermind the obvious fact is we pay more for CDs because of shipping costs all the way down under), even though we are now above parity and iTunes USA is $1 per track. ACCC can't do a thing either because its digital downloads)




E85 really needs to be much cheaper for the average motorist to get on board.

from my excel spreadsheet, 99 cents per litre you could save $440 per year using E85, whereas $1.17 for example would cost you $233 MORE per year to use E85.

[SSD-85]

Originally Posted by JC807

from my excel spreadsheet, 99 cents per litre you could save $440 per year using E85, whereas $1.17 for example would cost you $233 MORE per year to use E85.

Do those costs take into account the lesser energy efficiency of E85?

Although, thats a moot point from my opinion on this matter. Which is that Ethanols reduced efficiency compared to petrol is made redunant by the fact its renewable.

[Franco Cozzo]

Originally Posted by JC807

nevermind the obvious fact is we pay more for CDs because of shipping costs all the way down under),

I call BS, its expensive because its sold in Australia.

Anything to do with electronics is stupidly expensive here for no reason, games for example, dead space 2 is $110 in EB Games, I got it brand new for $53 AUD including shipping from PlayAsia.

[vztrt]

Originally Posted by irish2

The one benefit of E85 is it isn't made totally from oil. LPG is.

Our LPG actually comes from the natural gas fields.

[flappist]

Originally Posted by Scotty85

Do those costs take into account the lesser energy efficiency of E85?

Although, thats a moot point from my opinion on this matter. Which is that Ethanols reduced efficiency compared to petrol is made redunant by the fact its renewable.

Really?

Renewable eh?

And how is it made? Lots of electricity involved. And guess what we burn to make electricity.........

[SSD-85]

Originally Posted by flappist

Really?

Renewable eh?

And how is it made? Lots of electricity involved. And guess what we burn to make electricity.........

We burn molten rock by geothermal power which is limited only by the lifespan of this planet...Which is about as economically feasible as our future is going to get.

[pottery beige]

stick stuff in it so you cant drink it.....

[flappist]

Originally Posted by Scotty85

We burn molten rock by geothermal power which is limited only by the lifespan of this planet...Which is about as economically feasible as our future is going to get.

Oh that's a good idea.......

And where is this geothermal rock place in Australia?
Near one of our volcanoes?
Along one of our tectonic plate junctions?

You may have slightly more credibility as a greeny if you did not own 3 V8s........

According to CSIRO if we were to distill every single crop grown in Australia into ethanol we would still not be able to supply 10% or our fuel needs.........

But as with most greeny loony stories, facts only get in the way of the warm and fuzziness.......

[SSD-85]

Originally Posted by flappist

Oh that's a good idea.......

And where is this geothermal rock place in Australia?
Near one of our volcanoes?
Along one of our tectonic plate junctions?

You may have slightly more credibility as a greeny if you did not own 3 V8s........

According to CSIRO if we were to distill every single crop grown in Australia into ethanol we would still not be able to supply 10% or our fuel needs.........

But as with most greeny loony stories, facts only get in the way of the warm and fuzziness.......

Settle down flappyboy. I was merely suggesting a form of electricity generation that also supports your renewable argument, I couldve said nuclear but that aint technically renewable. And Greenies can suck the tailpipes of my 3 V8s. If I was wanting to be credible in that respect, I wouldnt dare support the use of Ethanol in the first place.

If CSIROs projections were correct, then what Brazil does must be an Act of god.

[aussie muscle]

Originally Posted by JC807

IMHO ethanol produced in this country should never be pegged (albeit lower total price) to petrol prices.

Unfortunately as a signatory to OPEC, we have no choice but to set it higher. it wouldn't take long to switch the majority of vehicles to E85 if it was 50 cents a litre.

[Spoony]

Interesting read but LPG surely should have been included (even a aftermarket liquid injected kit as falcon/commodores will be running later in the year). No doubt we'll see that when they come out though.

The only real + with E85 long term is it's renewable. But at what cost in producing it? As stated it's not really viable as a 100% fuel replacement, with land needed for food etc.

As far as oil dependance go, LPG is the answer, aust exports over 1/2 of its Natural Gas (where LPG is/can be sourced) and apparently has plenty of gas reserves?

Environmentaly (per energy) 20% less CO2 than petrol and apparently only 20% of the toxians emited by petrol (so I've read).
And at around 50% petrol price or less, using 15% more or so (liquid Inj) it's a noticable cost saver too.

Diesel as far as I know is 100% import dependant due to the lightness of aust crude oil or something.

While it's efficent to burn L/100km wise is not exactly clean.

Really, for Aust. LPG is surely the best solution for both enviroment and costs?

[JC807]

Originally Posted by Scotty85

Do those costs take into account the lesser energy efficiency of E85?

depending on from what the ethanol is produced, it has a great NET energy efficiency. corn, sugar cane, waste are all different.
yes, here is my spreadsheet:

[bobthebilda]

Originally Posted by JC807
IMHO ethanol produced in this country should never be pegged (albeit lower total price) to petrol prices.

Originally Posted by aussie muscle

Unfortunately as a signatory to OPEC, we have no choice but to set it higher. it wouldn't take long to switch the majority of vehicles to E85 if it was 50 cents a litre.

Autralia never has, and due to the ACCC, never will be a signatory to OPEC (Orgaisation of the Petroleum Exporting Countries). For one thing, we arent a net exporter of oil.

Crude oil prices come into (go out of) australia at what ever prices the buyer and seller want to agree to it (apart with various royalties and excises attatched).

Ethanol works in exactly the same way. If the ethanol manufacturer wants to sell it to a distributor for 10 cents a litre, there is nothing stopping them. Their is no link between the costs of making/selling crude oil or making ethanol.

The only link between both forms of energy, is that the Feds place various taxes (excises) on the fuels before they are sold to the public. At the moment, the excises are alot more on crude oil products than ethanol (To give the ethanol industry a chance to get started), By the feds have mandated that excises on ethanol will increase over time.

[irish2]

Originally Posted by vztrt

Our LPG actually comes from the natural gas fields.

It may come from natural gas fields but it is still a by product of petoleum. You can not make natural gas into LPG.

[Mr Hardware]

If you want a high octane, low calorific-value fuel, go LPG. Simple.

[vztrt]

Originally Posted by irish2

It may come from natural gas fields but it is still a by product of petoleum. You can not make natural gas into LPG.

No but you get different types of gas that comes out of gas fields. Instead of burning it off (like they did long ago) its now used for a few uses one being LPG.

[bobthebilda]

The two are different. In order to turn natural gas into a liquid, you need to take it down to minus 162 degrees celcius (obviously you dont see that any in cars or buses these days). LPG doesnt require the freezing bit. Also LPG is denser than air in its natural state, whereas natural gas is lighter than air.

LPG has a higher calorific value (94 MJ/m3 equivalent to 26.1kWh/m³) than natural gas (methane) (38 MJ/m3 equivalent to 10.6 kWh/m3), which means that LPG cannot simply be substituted for natural gas. In order to allow the use of the same burner controls and to provide for similar combustion characteristics, LPG can be mixed with air to produce a synthetic natural gas (SNG) that can be easily substituted. LPG/air mixing ratios average 60/40, though this is widely variable based on the gases making up the LPG. The method for determining the mixing ratios is by calculating the Wobbe index of the mix. Gases having the same Wobbe index are held to be interchangeable.

LPG-based SNG is used in emergency backup systems for many public, industrial and military installations, and many utilities use LPG peak shaving plants in times of high demand to make up shortages in natural gas supplied to their distributions systems. LPG-SNG installations are also used during initial gas system introductions, when the distribution infrastructure is in place before gas supplies can be connected. Developing markets in India and China (among others) use LPG-SNG systems to build up customer bases prior to expanding existing natural gas systems.