Gas Vs Petrol

[jayinoz]

Is putting you car on gas value for money?

If you drive a lot I am told- yes.

Supposedly Gas burns up a little faster than Petrol.

So if your car does approx. 11 km per litre on petrol it will do approx 10km on gas.

Now Gas is 12.99 bt per litre Vs 33bt for petrol.

Gas is supposed to create a larger spark at start causing greater wear and tear on your car than petrol.

You pay approx. 15000bt for conversion to gas in Thailand.

Gas is more enviro friendly.

Therefore you ROI should be between 10000km to 15000km, plus it may add some value to your car- maybe not.

If I am wrong in any of the above please correct me.

Interested to hear other thoughts and a vote...

[WarpSpeed]

I have it and in terms of savings I believe it's worth it but in terms of vehicle wear and tear the jury is still out from my point of view, admittedly I'm not fully up to specs on it yet though it's a new adventure.

Shopping around on used car sites I believe it does increase the value of your car in this market and with the added bonus of doing something good for the environment. So far I've yet to experience the mechanical draw backs and maybe I won't since I take better then average care of my cars but, time will tell..

Your information about the start up is new to me, so intended only as a learning process I'm curious to know how exactly would it be detrimental to get a hotter fire upon cold start? Can you tell me what damage that is supposed to create? I don't see any, but maybe I'm missing something.

My system which was in the car when I bought it was improperly installed and the gas injector was installed against the flow of air instead of with it so performance was terrible and gas was new to me but when I found that I knew it wasn't correct and changed it, now performance is indistinguishable from fuel/petrol. I did notice some melting damage done to some plastic parts and various covers inside my fuel injector housing indicating some sort of ignition outside of the combustion chamber.

I think this was due to the improper injector installation causing poor air and gas flow and why the car was bucking before I corrected it as it backfired up through the throttle valve. A gas backfire would not be like a fuel backfire it would be much less noticeable igniting less violently and loudly when it went off similar to lighting your stove in this case but the car would hesitate and buck like mine was doing.

It's hard to tell if it is still doing damage but I don't think so, I don't really like the injector located so far down stream from the intake though and would like to install a more direct injection system into each individual intake port past the throttle body not into the intake hose as it is now.. Mostly this would remove what is certain to be a performance drop off when using regular fuel as the injector severally restricts the air flow required down to about 2 inches diameter in my car from more then 3 and that's significant on any engine but most certainly a small bore engine. I have an auto feature which is supposed to turn on the gas from the fuel once it has reached operating temp. but not sure if it is working properly as it seems to take a long time to switch if it even does at all, hard to tell. I'd like to locate a set of installation instructions somewhere which specify the proper electrical hook up to be certain.

Conclusion.......I have plenty of my own questions to answer on this one before I can answer conclusively..

Edited May 18, 2010 by WarpSpeed

[fredob43]

The only drawback I can see is the room the gas tank take's up. Other than that it's a win win situation. All the taxi's use it so cant be that bad.

[WarpSpeed]

^Yes definitely a negative but for me that just brings my trunk down to the size of the average trunk around here so certainly manageable in a VW..

[VocalNeal]

You guys might like this.

series organiser TOCA has now told all teams running liquefied petroleum gas engines that they must fit 37mm air restrictors to their turbo inlets.

My truck has been on LPG since new. I do have the little oil injector, just to be on the safe side. Fuel cost is about 1.5 to 1.6 Baht per km. Tank fits nicely underneath out of view. CNG? no thank you.

[katabeachbum]

I have extensive experience with LPG in V8 yank petrol engines, and some experience blending diesel with LPG. My company used to import US trucks made in Canada to Europe.

Petrol engines do not run LPG properly until cooling water has reached 65 Centigrades, cause this is the needed temp in evaporator to work. Most electronic(usually Italian or Canadian) LPG systems starts engine automaticly on petrol, and switches to LPG when 65Centigrades is reached in coolingwater. A good electronic system uses the same fuel gauge for petrol and LPG, depending on whats being run. Engine also backfires easily on LPG before vacuum in airflow is reached.

Most engines are not designed for the higher combustion temperature with LPG, so premature damage to valves is common for highreving (over 5000rpm) engines with 4 valves. Most BKK taxis running LPG or CNG has a modified 1600cc engine, similar to the engine provided by Toyota Altis CNG.

LPG is presently subsidised in LOS as cooking gas, and new taxis are no longer allowed to install LPG. They are to install CNG as the future fuel for LOS, in addition to biodieselblend and gasohol.

For a second hand car, I would pay less if its got LPG fitted, due to reduced lifetime for engine and petrol system often clogged

[BSJ]

The older systems with a mixer in the air inlet aren't the best to use in this day and age. What you should be looking at is an LPG injection

system like the Prins Vapour Sequential Injection System. My friend, who is a qualified gas fitter, has fitted many at his garage. They are so much better in terms of performance and economy there is no comparison.

http://www.parnell.com.au/index.php?option...7&Itemid=41

[WarpSpeed]

The older systems with a mixer in the air inlet aren't the best to use in this day and age. What you should be looking at is an LPG injection

system like the Prins Vapour Sequential Injection System. My friend, who is a qualified gas fitter, has fitted many at his garage. They are so much better in terms of performance and economy there is no comparison.

http://www.parnell.com.au/index.php?option...7&Itemid=41

Well that was what I was thinking, thanks for the link..

*edit* After checking the link 2 problems I see, no price listings and no official installers listed in Thailand so is this product even available here?

Edited May 18, 2010 by WarpSpeed

[ClareQuilty]

I really wouldn't even consider changing. In the first place my car is 27 years old, and in the second, I don't drive all that much.

But in any car I would be averse to a gas conversion due to the potential damage to the engine for a few baht a month saved.

[WarpSpeed]

I really wouldn't even consider changing. In the first place my car is 27 years old, and in the second, I don't drive all that much.

But in any car I would be averse to a gas conversion due to the potential damage to the engine for a few baht a month saved.

So then you don't have much to loose on a 27 year old car that you don't drive very much....But enlighten us, just what potential damage are you referring to that would be such a losing proposition over money saved?

[ClareQuilty]

So then you don't have much to loose on a 27 year old car that you don't drive very much....But enlighten us, just what potential damage are you referring to that would be such a losing proposition over money saved?

Actually I would have everything to lose. The car cost me just 50,000, and there is virtually no chance I could afford another, nor especially one of the very expensive newer ones. This car is very valuable to me as it allows me to have the use of a car the once or twice a week I need one - rainy days, visiting a nearby town, etc. In a sense the car is 'irreplaceable', and it certainly wouldn't be worth risking losing its use for even a few hundred baht per month.

As for potential damage I've always been told that there are many parts in the engine and fuel system which are damaged by using fuels the engine was not built for.

Edited May 18, 2010 by ClareQuilty

[WarpSpeed]

So then you don't have much to loose on a 27 year old car that you don't drive very much....But enlighten us, just what potential damage are you referring to that would be such a losing proposition over money saved?

Actually I would have everything to lose. The car cost me just 50,000, and there is virtually no chance I could afford another, nor especially one of the very expensive newer ones. This car is very valuable to me as it allows me to have the use of a car the once or twice a week I need one - rainy days, visiting a nearby town, etc. In a sense the car is 'irreplaceable', and it certainly wouldn't be worth risking losing its use for even a few hundred baht per month.

As for potential damage I've always been told that there are many parts in the engine and fuel system which are damaged by using fuels the engine was not built for.

Ok so nothing specific then just generally inexplicable and irrational fear, oh, now I understand ...

Edited May 18, 2010 by WarpSpeed

[JohnLeech]

The only drawback I can see is the room the gas tank take's up. Other than that it's a win win situation. All the taxi's use it so cant be that bad.

Is there any reason why gas conversions in Thailand, even including the factory fitted Chevy ones, do not use a "polo" shape tank in the spare wheel well, as I believe is far more common in the UK and Europe?

I can see that they may be a bit smaller, but fitting a big tank in something like a Chevy Captiva or Optra Estate surely means that you lose virtually all the practicality and point of that sort of car? Its the main thing that puts me off, certainly.

[katabeachbum]

The only drawback I can see is the room the gas tank take's up. Other than that it's a win win situation. All the taxi's use it so cant be that bad.

Is there any reason why gas conversions in Thailand, even including the factory fitted Chevy ones, do not use a "polo" shape tank in the spare wheel well, as I believe is far more common in the UK and Europe?

I can see that they may be a bit smaller, but fitting a big tank in something like a Chevy Captiva or Optra Estate surely means that you lose virtually all the practicality and point of that sort of car? Its the main thing that puts me off, certainly.

good point, I v never seen a sparewheel tank here. For CNG they are almost impossible to make due to the high storage pressure, but for LPG they are very common in Europe. In a 2008-2010 Honda Accord a sparewheeltank could be like 80 liters under the trunk floor.

[katabeachbum]

So then you don't have much to loose on a 27 year old car that you don't drive very much....But enlighten us, just what potential damage are you referring to that would be such a losing proposition over money saved?

Actually I would have everything to lose. The car cost me just 50,000, and there is virtually no chance I could afford another, nor especially one of the very expensive newer ones. This car is very valuable to me as it allows me to have the use of a car the once or twice a week I need one - rainy days, visiting a nearby town, etc. In a sense the car is 'irreplaceable', and it certainly wouldn't be worth risking losing its use for even a few hundred baht per month.

As for potential damage I've always been told that there are many parts in the engine and fuel system which are damaged by using fuels the engine was not built for.

Ok so nothing specific then just generally inexplicable and irrational fear, oh, now I understand ...

burned valves being most common, due to the much higher combustion temperature and lack of lubrication from petrol. for a 27 year old designed for leaded fuel, LPG is no no without 2-strokeoil injection

[PattayaParent]

Now Gas is 12.99 bt per litre Vs 33bt for petrol.

If I am wrong in any of the above please correct me.

I filled up yesterday and the cost of Gasohol 91 was 31.12 per litre.

But it's not only the cost of the fuel that is important, you need to know how many kms per litre.

So how many litres needed to fill up a gas tank, what's the cost and how far can you go on it before a refill compared to the same for petrol?

[katabeachbum]

Now Gas is 12.99 bt per litre Vs 33bt for petrol.

If I am wrong in any of the above please correct me.

I filled up yesterday and the cost of Gasohol 91 was 31.12 per litre.

But it's not only the cost of the fuel that is important, you need to know how many kms per litre.

So how many litres needed to fill up a gas tank, what's the cost and how far can you go on it before a refill compared to the same for petrol?

for petrol engines less than 3000cc using old fashioned vacuum system expect 30% more fuel/km. electronic controlled injection system, expect 10% more fuel/km. 10-30% drop in power for non turbo engines. f

for large V8 and V10s with electronic injection systems, milage and power is same

for turbo intercooled petrolengines power can increase due to the cool LPG entering combustion chamber allowing more O2 in air.

for turbo intercooled diesel engines running 30-50% LPG bledned with diesel expect much more power and good increase in milage in addition to clean emission

My 2000 Ford Excursion 6,8 V10 had a 150 litres netto (170 litres brutto) LPG tank and covered 500km on 150 litres. Not bad for 300hp and 3,5 tons 4X4. Slightly better milage on petrol only. Power same, but running LPG removed speedlimiter at 160kmh. Canadian Electonic system always starting on petrol and switching automaticly to LPG after 2 minutes or when coolantwater reached 65 Centigrades. Running LPG, emission was very clean. Never had a LPG/petrol problem, and the fuel costs on LPG where 40% of petrol

Edited May 19, 2010 by katabeachbum

[PattayaParent]

I drive a Toyota Vios 1500cc engine and a petrol fill up of about 39 litres costs around 1,250 Baht from which I get around 650 to 670kms.

Is it only 15,000 Baht for the conversion now? I'm sure I read on here before more like 40,000 Baht.

[WarpSpeed]

So then you don't have much to loose on a 27 year old car that you don't drive very much....But enlighten us, just what potential damage are you referring to that would be such a losing proposition over money saved?

Actually I would have everything to lose. The car cost me just 50,000, and there is virtually no chance I could afford another, nor especially one of the very expensive newer ones. This car is very valuable to me as it allows me to have the use of a car the once or twice a week I need one - rainy days, visiting a nearby town, etc. In a sense the car is 'irreplaceable', and it certainly wouldn't be worth risking losing its use for even a few hundred baht per month.

As for potential damage I've always been told that there are many parts in the engine and fuel system which are damaged by using fuels the engine was not built for.

Ok so nothing specific then just generally inexplicable and irrational fear, oh, now I understand ...

burned valves being most common, due to the much higher combustion temperature and lack of lubrication from petrol. for a 27 year old designed for leaded fuel, LPG is no no without 2-strokeoil injection

It seems that a good synthetic and or oil additive should guard against that, they stand up better to higher temps and provide better residual lubrication then conventional oil... Agreed cheap oil and improper maintenance will otherwise cause problems....

If valves are burning no oil is going to prevent that, only a change of valve material or fuel mixture adjust to lean the mixture in the case of LP which is part of the conundrum as most engines (especially small bore) require a richer mixture of regular fuel to perform well especially at highway speeds and this is this biggest problem I can see with a combined system. There is an available system as has been noted, that interferes as little as possible with the factory fuel system and that system would be a direct injection multiport type and not what is commonly used here obviously due to expense, but this system which I doubt anyone here is using currently as their guide is the only way to really make a valid comparison..

Edited May 19, 2010 by WarpSpeed

[WarpSpeed]

I drive a Toyota Vios 1500cc engine and a petrol fill up of about 39 litres costs around 1,250 Baht from which I get around 650 to 670kms.

Is it only 15,000 Baht for the conversion now? I'm sure I read on here before more like 40,000 Baht.

12.99 for LP? I've never paid more then 11.90 and that was in the sticks in Chon Buri a couple of weeks ago has it gone up that much since then? Still your point is taken, here in Bangkok it is around 11.35 at my neighborhood station... I have never filled my tank with fuel and made along drive on it only LP but I know cars of this engine size and fuel consumption like the back of my tush so I don't need an actual figure from this particular car as I can average to see that my LP mileage is considerably better with LP..

As for performance this is another reason a level comparison is not possible as with the LP injector installed, the car is undoubtedly not getting a full breath with every stroke as the injector being up stream causes a severe restriction, preventing an equal comparison to be had on either performance or mileage as all things are not equal..

Edited May 19, 2010 by WarpSpeed

[katabeachbum]

It seems that a good synthetic and or oil additive should guard against that, they stand up better to higher temps and provide better residual lubrication then conventional oil... Agreed cheap oil and improper maintenance will otherwise cause problems....

If valves are burning no oil is going to prevent that, only a change of valve material or fuel mixture adjust to lean the mixture in the case of LP which is part of the conundrum as most engines (especially small bore) require a richer mixture of regular fuel to perform well especially at highway speeds and this is this biggest problem I can see with a combined system. There is an available system as has been noted, that interferes as little as possible with the factory fuel system and that system would be a direct injection multiport type and not what is commonly used here obviously due to expense, but this system which I doubt anyone here is using currently as their guide is the only way to really make a valid comparison..

valves can only be cooled and lubricated by fuel, so no synthetic oil or oil additive can prevent them burning.

most of piston is also only cooled by fuel, leading us to next most common failure on LPG engines. burned holes in pistons, and not to mention burned seats for valves, and cracked heads. all due to increased combustion temperature. it seems that 4 pots with less power, like the protons, are able to survive longer running LPG than for instance Hondas 2000cc 155 hp.

and again, large V8 and V10s with 2 valves and lets say max 50hp/1000cc seem to run LPG for ages without problems, as long as petrolsystem is being used for every start up.

[WarpSpeed]

Funny you answered again as the more I thought about it the more I realized that the burned valves you speak of in a dual-fuel system have virtually nothing to do with the LP temps generated but rather the leaned out fuel mixture when in regular fuel mode due to the air flow restriction of the LP injector.....Again why a multi-injector system upstream from the throttle valve is required...LP gets the blame though because it seems to be the commonality but the latter is never considered as being the real problem..

[WarpSpeed]

It seems that a good synthetic and or oil additive should guard against that, they stand up better to higher temps and provide better residual lubrication then conventional oil... Agreed cheap oil and improper maintenance will otherwise cause problems....

If valves are burning no oil is going to prevent that, only a change of valve material or fuel mixture adjust to lean the mixture in the case of LP which is part of the conundrum as most engines (especially small bore) require a richer mixture of regular fuel to perform well especially at highway speeds and this is this biggest problem I can see with a combined system. There is an available system as has been noted, that interferes as little as possible with the factory fuel system and that system would be a direct injection multiport type and not what is commonly used here obviously due to expense, but this system which I doubt anyone here is using currently as their guide is the only way to really make a valid comparison..

valves can only be cooled and lubricated by fuel, so no synthetic oil or oil additive can prevent them burning. My valves get cooled by oil flow as does every engine I know with the exception of the head and seats which are made of material to withstand most higher temps, don't know what engine you have?

most of piston is also only cooled by fuel, leading us to next most common failure on LPG engines. burned holes in pistons, and not to mention burned seats for valves, and cracked heads. all due to increased combustion temperature. it seems that 4 pots with less power, like the protons, are able to survive longer running LPG than for instance Hondas 2000cc 155 hp.

Mentioning that again reinforces to me that it is more due to the change back and forth between LP and regular fuel requiring opposing stoichiometric fuel mixture settings then it is the LP alone as the culprit, as those (Honda) engines perform at much higher RPMS which tend to lean out the mixture more in small bore if not properly adjusted..

and again, large V8 and V10s with 2 valves and lets say max 50hp/1000cc seem to run LPG for ages without problems, as long as petrolsystem is being used for every start up.

Edited May 19, 2010 by WarpSpeed

[katabeachbum]

Funny you answered again as the more I thought about it the more I realized that the burned valves you speak of in a dual-fuel system have virtually nothing to do with the LP temps generated but rather the leaned out fuel mixture when in regular fuel mode due to the air flow restriction of the LP injector.....Again why a multi-injector system upstream from the throttle valve is required...LP gets the blame though because it seems to be the commonality but the latter is never considered as being the real problem..

disagree

most LPG engines run very rich LPG mix as a vacuum system adding LPG in engines airintake. thus the decreased milage running LPG. most Dual fuel run less than 1% on petrol, and airflow is not restricted with a good designed aluminum LPG distributor/LPG feeder.

The 2 decades of experience with LPG I have on a couple of hundred units, burned valves and pistons and occational cracked head has been believed caused by the higher combustion temperature of LPG over petrol.

CNG has much higher combustion temperature, and all manufactorers find it needed to improve quality of engine parts to keep 100k km warranty.

Electronic controlled injection LPG/CNG has the same combustion temp probs, but has no effect on airflow running petrol only

Edited May 19, 2010 by katabeachbum

[WarpSpeed]

Horse pucks!! Plain and utter <deleted>!! There's a huge drop off in performance and air intake when using regular fuel with those LP injectors even if the restrictor was only mm's smaller and in this case it is significantly more restrictive you just can't notice the diff if it's installed because you have nothing to compare it against in real world applications. There is no such thing as a well made LP injector to any such spec that is installed down stream of the throttle body. It's because of the drop off that so many RACING organizations use restrictors as an equalizing tool..

Where you're still missing the point is that you are focusing in on the LP being the cause of the failures and damage and not considering or in fact dismissing that it's the incompatible nature of stoichiometric air/fuel ratio to LP stoichiometric ratios and that they are actually on opposite ends of the spectrum and therefore blaming the LP because it is the part that has been changed in that equation..

Electronic controlled injection LPG/CNG has the same combustion temp probs, but has no effect on airflow running petrol only

This is what I've been saying all along.. But where mechanical failures are concerned this system has not been out long enough to come to that conclusion definitively..

Edited May 19, 2010 by WarpSpeed

[katabeachbum]

Horse pucks!! Plain and utter <deleted>!! There's a huge drop off in performance and air intake when using regular fuel with those LP injectors even if the restrictor was only mm's smaller and in this case it is significantly more restrictive you just can't notice the diff if it's installed because you have nothing to compare it against in real world applications. There is no such thing as a well made LP injector to any such spec that is installed down stream of the throttle body. It's because of the drop off that so many RACING organizations use restrictors as an equalizing tool..

Where you're still missing the point is that you are focusing in on the LP being the cause of the failures and damage and not considering or in fact dismissing that it's the incompatible nature of stoichiometric air/fuel ratio to LP stoichiometric ratios and that they are actually on opposite ends of the spectrum and therefore blaming the LP because it is the part that has been changed in that equation..

Electronic controlled injection LPG/CNG has the same combustion temp probs, but has no effect on airflow running petrol only

This is what I've been saying all along.. But where mechanical failures are concerned this system has not been out long enough to come to that conclusion definitively..

1996 we installed electronic controlled injection LPG on Honda and Toyota taxis. Both car manufactorers had to admit their valves and pistons where not up to the increased combustion temp, and all burned valves within a year. No restriction in airflows on these units, they did 70-150k km a year, and used like 2 tanks of petrol a year for start up engine.

After burned valves we increased petrol running time at start up, and programmed petrol running 5 minutes an hour and they survived

I d say 14 years is long enough to establish why there are mechanical failures.

The manufactorers have faced this problem, and as said before cars designed for LPG or CNG come with other materials in some engine parts. Toyota Corolla Altis 1,6 CNG is one example.

Toyotas 3,0 V6 worked fine without petrol though.

cars running E85 has also dealt with engineproblems due to reduced lubricant in fuel, and has replaced similar parts to survive. They dont have any reduction of airflow either.

[JohnLeech]

I drive a Toyota Vios 1500cc engine and a petrol fill up of about 39 litres costs around 1,250 Baht from which I get around 650 to 670kms.

The techncal debate is beyond me, so this is the only post that really suprised me. You're getting over 17 kms per litre, which seems a fantastic mileage; I get no more than 13 (14 on a long trip) from my Yaris G (similar engine) and slightly less from my Nissan NV, which seems about average. Even the supposedly "eco" Nissan March apparently only gets that much if you turn the aircon off - any tips on how you do it?

[WarpSpeed]

Horse pucks!! Plain and utter <deleted>!! There's a huge drop off in performance and air intake when using regular fuel with those LP injectors even if the restrictor was only mm's smaller and in this case it is significantly more restrictive you just can't notice the diff if it's installed because you have nothing to compare it against in real world applications. There is no such thing as a well made LP injector to any such spec that is installed down stream of the throttle body. It's because of the drop off that so many RACING organizations use restrictors as an equalizing tool..

Where you're still missing the point is that you are focusing in on the LP being the cause of the failures and damage and not considering or in fact dismissing that it's the incompatible nature of stoichiometric air/fuel ratio to LP stoichiometric ratios and that they are actually on opposite ends of the spectrum and therefore blaming the LP because it is the part that has been changed in that equation..

Electronic controlled injection LPG/CNG has the same combustion temp probs, but has no effect on airflow running petrol only

This is what I've been saying all along.. But where mechanical failures are concerned this system has not been out long enough to come to that conclusion definitively..

1996 we installed electronic controlled injection LPG on Honda and Toyota taxis. Both car manufactorers had to admit their valves and pistons where not up to the increased combustion temp, and all burned valves within a year. No restriction in airflows on these units, they did 70-150k km a year, and used like 2 tanks of petrol a year for start up engine.

After burned valves we increased petrol running time at start up, and programmed petrol running 5 minutes an hour and they survived

This was more about initial technical tuning on newer technology though and not about the current day issues which have mostly been worked out in this very type of development years ago.. The systems available here do not have any such tuning available which is exactly what I've been saying they aren't advanced enough they are just expedient, affordable kits..

I d say 14 years is long enough to establish why there are mechanical failures.

The manufactorers have faced this problem, and as said before cars designed for LPG or CNG come with other materials in some engine parts. Toyota Corolla Altis 1,6 CNG is one example.

Of course they do as the required intake is completely different too.. CNG is not intended as a conversion application nor is it dual fuel..

Toyotas 3,0 V6 worked fine without petrol though.

cars running E85 has also dealt with engineproblems due to reduced lubricant in fuel, and has replaced similar parts to survive. They dont have any reduction of airflow either.

Yeah and the leaded cars of yesteryear also had problems with unleaded fuel when it was first introduced so what's your point? And the problem with this is that your data is 14 years old while technology has moved along nicely. I'm referring to the current systems which have only been developed over the last couple of years.. You are also not comparing equally what is available or more commonly applied here in Thailand with the system you installed somewhere in Europe. The entire technology is new here en mass within the last couple of years due to the increased cost of fuel and the governments subsequent discontinuing of the subsidies suddenly every mom and pop shop was installing them....

Edited May 19, 2010 by WarpSpeed

[PattayaParent]

I drive a Toyota Vios 1500cc engine and a petrol fill up of about 39 litres costs around 1,250 Baht from which I get around 650 to 670kms.

The techncal debate is beyond me, so this is the only post that really suprised me. You're getting over 17 kms per litre, which seems a fantastic mileage; I get no more than 13 (14 on a long trip) from my Yaris G (similar engine) and slightly less from my Nissan NV, which seems about average. Even the supposedly "eco" Nissan March apparently only gets that much if you turn the aircon off - any tips on how you do it?

Yeah, the techie stuff may as well be written in Klingon!

My wife's yaris only gets about 550~600kms tops from a tank of petrol so similar to you.

Tips? Well I don't drive fast, choose a route to / from work that minimises stop/go driving and as the AC is very good I only need to have it on 1/4 cooling with fan speed 1.

The Yaris needs full cooling and fan speed 2 to keep it cool.

[katabeachbum]

CNG is not intended as a conversion application nor is it dual fuel..

CNG is presently the most common conversion, and except for Tatas pickup they are all dual fuel