Savings with LPG fuel vs Petrol

[CrossBones]

Hi

On a 4 cylinder engine, and current prices of LPG and Petrol in Thailand. What kind of savings can i expect with LPG? 

For various reasons I will do a lot of engine idling as well (its a camper van).

 

Thanks

[MJCM]

2 things.

 

1- LPG Cars need more fuel to run the same KM's as a Petrol Car. (I am not 100% sure, but I guess it's something like 15-20% more fuel compared to Petrol)

2- Does the Car already have the LPG. Conversion. If not also consider the price of this.

 

Edited May 8, 2023 by MJCM
Changed some wording

[Captor]

50 minutes ago, MJCM said:

2 things.

 

1- LPG Cars need more fuel to run the same KM's as a Petrol Car. (I am not 100% sure, but I guess it's something like 15-20% more fuel compared to Petrol)

2- Does the Car already have the LPG. Conversion. If not also consider the price of this.

 

It is 10% more LPG. Or you could say/think that the engine is 10% weaker with LPG.

[Lacessit]

As a previous poster has said, 15-20% increased fuel consumption.

 

I can't speak for the cost of LPG conversion in Thailand, in Australia IIRC I recouped conversion cost in about 3 years. It depends on yearly kilometres of travel.

 

LPG makes for higher cylinder head temperatures, and has no lubricant properties as petrol and diesel do. I used to run the system on the basis of one quarter of a tank to every tank of LPG.

 

Complete conversion to LPG would be risky, unless the engine valve seats are specially hardened. Better to stay with a dual fuel system.

[brianthainess]

2 hours ago, Captor said:

It is 10% more LPG. Or you could say/think that the engine is 10% weaker with LPG.

I never noticed any difference in power with LPG, an old auto NV 

O-100klph 8.3 seconds on LPG with A/C on 2up.

[brianthainess]

2 hours ago, Lacessit said:

As a previous poster has said, 15-20% increased fuel consumption.

 

I can't speak for the cost of LPG conversion in Thailand, in Australia IIRC I recouped conversion cost in about 3 years. It depends on yearly kilometres of travel.

 

LPG makes for higher cylinder head temperatures, and has no lubricant properties as petrol and diesel do. I used to run the system on the basis of one quarter of a tank to every tank of LPG.

 

Complete conversion to LPG would be risky, unless the engine valve seats are specially hardened. Better to stay with a dual fuel system.

They are all dual systems, LPG conversions start on petrol no petrol and it won't start, as for 'higher cylinder temperature' overhead cams don't seem to have a problem.

[brianthainess]

I had a conversion done 9yrs ago never had a problem with it, Fuel prices have changed but to fill with petrol *at the time* was 1,000bht LPG was 500b well worth it the 20k conversion paid for it's self in 18mths , The only downfall i have now is every year when the vehicle test is due it has to have an LPG test at a cost of 1,500 B !!  and next year a new tank required after 10yrs. And of course on idle no CO2 fumes is a big benefit. There are 2 different tank choices Donut that fits your spare wheel space or a normal tank.

[Lacessit]

1 hour ago, brianthainess said:

They are all dual systems, LPG conversions start on petrol no petrol and it won't start, as for 'higher cylinder temperature' overhead cams don't seem to have a problem.

Some vehicle manufacturers have cars which are dedicated LPG, without a petrol tank in sight. AFAIK they start on LPG without petrol assistance.

They should, the flash point of LPG is lower.

On the vehicles I had converted, there was a bailout which enabled starting on LPG if the petrol tank was empty.

IIRC, cylinder head temperatures are 300 C for petrol, 400 C for LPG. CNG is even higher at 600 C.

I'm not sure what overhead cams have to do with valve seats, except for being connected via the valves.

[Kwasaki]

10 hours ago, CrossBones said:

(its a camper van)

Diesel engine swap best.