Is there a basic rule i.e mpg doubles? or is it one and a half?

Basically I'm trying to weigh up the cost (which is around £1.5k) against the saving over a cars 4-5 year ownership length.

:go:

i ran a 2L nissan serena on gas and it was about 55mpg you have to weigh up the car and engine and how you drive
how old is the car
has it been looked after
if a car runs badly on normal fuel it will run badly or worst on LPG

I am led to believe it is very similar MPG (someone might like to confirm this) but at the moment and for the forseeable future the LPG will remain at half the price of petrol.

The government offer incentives and might help to fund the cost. I believe not all cars are able to be converted.

Here is details of my car with a conversion quote including savings and investments

Vehicle: Honda Civic 1.6 SR Coupe 2d 1590cc
LPG System Greenfuel (20314)
Tank Toroidal
Cost of Conversion £1,730.00 + VAT
Net Cost of Conversion £2,032.75 inc VAT
Petrol Spend PA £1,483.54 per year
LPG Spend PA £814.51 per year
Saving PA £669.03 per year
Return on Investment 33%
CO2 Saving 0.76 Tonnes
Approved by top 20
insurance companies Yes

This is based on my car doing 12,000 miles a year. I would need to own my car for 3 years before i got any benefit.

See info here: http://www.greenfuel.org.uk/

so a 33% turnaround on a 1.6, I ws thinking of my next car being 3.0 plus and therefore saving money on fuel a necessity. Would this reduce the percentage accordingly? i.e 17.5% or does it not work like this?

You slightly loose some MPG but the fuel itself is so much cheaper.

Roughly 50% better in real money terms.

How much do you spend a year on fuel ?

It doenst matter at the moment, i only have a 1.2 but for my next car I invisage using around £30 a week which will soon build up. And that assuming the prices of petrol are the same in 2-3 years time which they wont be! Nightmare scenario really. Thanks for the info though

thats £1560 per year, you would save approx £500 per year so if it costs £1,000 to have it fitted then after 2 years your saving big time

My mate has a bmw 740 which has a gas conversion and he puts about £20 of gas in a week think if he ran it on petrol he is looking at more than double.

If you are keeping the car its well worth doing.

I might buy a M535i and have the conversion done but i will have to see.

Might be woth me getting one take a look at my qoute me doing 30000 a year:
Vehicle: Jaguar XJ6 3.2 S Saloon 4d 3239cc
LPG System Greenfuel (19196)
Tank Toroidal
Cost of Conversion £1,900.00 + VAT
Net Cost of Conversion £2,232.50 inc VAT
Petrol Spend PA £6,743.37 per year
LPG Spend PA £3,702.31 per year
Saving PA £3,041.06 per year
Return on Investment 136%
CO2 Saving 4.67 Tonnes
Approved by top 20
insurance companies Yes

I ran my range rover for 2 years on gas , i found that i the mpg droped by 2-5 mpg but the gas was so much less per litre it didn't matter . Try A1 Auto gas in liverpool , £1700 +vat sounds a lot .