LPG vs Petrol

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Was chatting witha friend recently, who got a LPG conversion kit for his maruti van.

He said after a while he went back to petrol because he did get much benefit from it economically. for the same amount of money he'd get further with petrol.

Which surprised me as petrol is like Rs.55/litre vs Rs.35/litre for LPG. Energy wise LPG release 70% of the energy you'd get from petrol for the same volume.

Either conversion kits are horribly inefficient or something else was wrong ?

Maybe if the engine was designed just for LPG instead of using a petrol engine with a conversion kit then it would have worked out better.

What to make of this :huh:
 
I had used LPG, on a maruti 800 for long time. Even before the days of licensed kits (RTO approved kits).

The LPG vehicle is cheaper to run only if the LPG used is sourced through the subsidized cylinders, if you go to a commercial pump and fill the tank than the saving is not substantial.

There is no bearing on running of vehicle due to LPG. What I heard through technicians, older carburetor based engines designs ran very well with LPG while newer MPFI engines had some sort of FE problems. (I am no techie about this posting just what I heard).

Now a days with availability of CNG increasing here in Surat people are prefering CNG over LPG.
 
medpal said:
I had used LPG, on a maruti 800 for long time. Even before the days of licensed kits (RTO approved kits).

The LPG vehicle is cheaper to run only if the LPG used is sourced through the subsidized cylinders, if you go to a commercial pump and fill the tank than the saving is not substantial.
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Yeah, this is exactly the scenario i was describing. I think using subsidised LPG would be illegal because its not subsidised for vehicles but for cooking :)

But if you could source it then yeah, nice bonus.

medpal said:
There is no bearing on running of vehicle due to LPG. What I heard through technicians, older carburetor based engines designs ran very well with LPG while newer MPFI engines had some sort of FE problems.
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Hmm, this van i think might be 5-10 years maybe. Fuel injected has been a round lot longer than that so maybe that is why he did not notice too much difference.

The figures made me think otherwise. You get 30% less energy but pay 60% less therefore there should be a saving of at least 30% (ideally). Maybe half that in reality, so 10-15% savings. But if the process itself isn't efficient then everything goes for a toss if used with a FI engine.

medpal said:
(I am no techie about this posting just what I heard).
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Pretty good for a non-techie :cool2:

I wonder how much more the real 'techies' can add.

medpal said:
Now a days with availability of CNG increasing here in Surat people are prefering CNG over LPG.
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Ahh, i think there was some confusion on my part here, by me assuming LPG to be CNG. Different animal completly CNG :)

CNG has half the energy of LPG so that means only a third of petrol. So costwise it should be much less than a third of the price of petrol for the same energy released. Otherwise the only advantage CNG offers over petrol is less pollution which isn't much of an incentive to use for consumers.

And therein lies the rub, if CNG could really compete with petrol with all the efficiency claims you hear for CNG then it should be selling like hotcakes and not require any govt subsidies whatsoever. However there may be an argument in favour if used in public transport where daily miles covered is much more than individual vehicles.
 
blr_p said:
Ahh, i think there was some confusion on my part here, by me assuming LPG to be CNG. Different animal completly CNG :)

CNG has half the energy of LPG so that means only a third of petrol. So costwise it should be much less than a third of the price of petrol for the same energy released. Otherwise the only advantage CNG offers over petrol is less pollution which isn't much of an incentive to use for consumers.

And therein lies the rub, if CNG could really compete with petrol with all the efficiency claims you hear for CNG then it should be selling like hotcakes and not require any govt subsidies whatsoever. However there may be an argument in favour if used in public transport where daily miles covered is much more than individual vehicles.
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Your details of CNG / LPG of some percentages of energy than petrol went over my head :P.

The scenario here turns out like this.
A wagon R running on :
Petrol - FE 12 kmpl cost nearly 5 Rs. / Km
LPG - FE (I dont know in terms of KMPL) but in Rs terms it turns out to be 3.5-3.7 / KM
CNG - 1.5 - 1.75 Rs. / KM

Here is situation is such that, LPG pumps are very few and you have to go long distance while a single filling last longer.

CNG is available within city limits abundantly due to 100% pipe line coverage of gas and also whole of NH 8 in gujarat upto Mehsana in north, Vapi in south and Jamnagar in west have CNG supply now.

In a heavy running vehicle even Diesel turns out to be costlier.

Only disadvantage of CNG/ LPG is nonexistant boot space in hatchbacks and reduced space in sedans.
 
i did read this once that on one hand where the CNG/LPG are more fuel efficient, on the other they are basically DRY fuel for the machinery.

Petrol still plays a role in lubricating parts it comes in contact with and hence the parts suffer somewhat less friction while working hence have a prolonged life.

Maybe somebody else will shed some more light on the veracity of the above info.
 
not sure about LPG but a friend of mine using CNG for his Chev Sparks is getting rather better economy than petrol.
 
yes cng gives better fuel efficiency than petrol, case in point my petrol innova which gives petrol=7 kmpl & cng=9.5 kmpl in city. So cost wise cng is more than 2 times cheaper than petrol
 
medpal said:
Your details of CNG / LPG of some percentages of energy than petrol went over my head :P.
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Energy content of various fuels

Was thinking back to high school chemistry, how much energy produced etc.

Petrol......34.8 MJoules/lt
LPG....... 26.8 MJ/lt
CNG........25.3 MJ/lt

I was wrong about CNG having half the energy of LPG!

medpal said:
The scenario here turns out like this.
A wagon R running on :
Petrol - FE 12 kmpl cost nearly 5 Rs. / Km
LPG - FE (I dont know in terms of KMPL) but in Rs terms it turns out to be 3.5-3.7 / KM
CNG - 1.5 - 1.75 Rs. / KM
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Where did you get these figures from ?

Looking at them
LPG gives a 30% saving over petrol
CNG gives a 300% saving over petrol.

Why aren't we seeing more CNG vehicles ?

medpal said:
Here is situation is such that, LPG pumps are very few and you have to go long distance while a single filling last longer.

CNG is available within city limits abundantly due to 100% pipe line coverage of gas and also whole of NH 8 in gujarat upto Mehsana in north, Vapi in south and Jamnagar in west have CNG supply now.
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Very good

medpal said:
In a heavy running vehicle even Diesel turns out to be costlier.
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Right, so these are the vehicles that could benefit most from CNG.

medpal said:
Only disadvantage of CNG/ LPG is nonexistant boot space in hatchbacks and reduced space in sedans.
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CNG will require a tougher bigger tank, LPG will be fine as its liquefied already. The autos here carry a small LPG cylinder at the back, and they use a simple two stroke engine so they get the savings that a fuel injected engine would not deliver.
 
@blr_p here in Surat, there is tremendous amount of CNG vehicles. All the autos are compulsorily CNG so too are city buses.

There are so many cars, commercial vehicles running on CNG almost every one who thinks of buying a car for city purposes goes for petrol and then converts to CNG.
 
blr_p said:
Energy content of various fuels

Was thinking back to high school chemistry, how much energy produced etc.

Petrol......34.8 MJoules/lt

LPG....... 26.8 MJ/lt

CNG........25.3 MJ/lt

I was wrong about CNG having half the energy of LPG!

Where did you get these figures from ?

Looking at them

LPG gives a 30% saving over petrol

CNG gives a 300% saving over petrol.

Why aren't we seeing more CNG vehicles ?

Very good

Right, so these are the vehicles that could benefit most from CNG.

CNG will require a tougher bigger tank, LPG will be fine as its liquefied already. The autos here carry a small LPG cylinder at the back, and they use a simple two stroke engine so they get the savings that a fuel injected engine would not deliver.
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most entry level vehicles offer that option now.

BEST in mumbai has a lot buses running on that.

not sure about 300% but effectively it is twice economical from what my friend says.

i even had spoken with alot of auto ric drivers bout how economical it is and they all made a point that it makes a lot of difference to them.
 
With the lpg cylinders used for cooking the cost is abt 1-1.5 per litre.

The problem is sourcing them so often. I know of a driving school guy who uses it. He takes it directly from some company where they pay cash and get it directly.

--- Updated Post - Automerged ---

The vehicle is a maruti 800 :P
 
You have to work out convenience vs cost

The problem is how easily can you fuel up. How varied is your travel. If you do not travel very far and there are CNG stations nearby it works.

Otherwise petrol is the most convenient and the difference will show in how free you are to go wherever you want.
 
LPG kits can switch on the fly between pertrol and Lpg, So you're good to go incase you want a long ride.

Also I read something about the mileage varying with speed of the car.
 
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