Hi
My way of thinking is if I'm paying 72p per litre for gas, but loosing 20% efficiency compaired to running on petrol then I am running my car as if petrol was currently costing 86.4p per litre (as I'm having to use 20% more fuel to cover the same milage).
i.e 72+20%=86.4
Are my calculations right?
So to travel the same distance would use 20% more gas than petrol.
If my car used 10 litres of petrol to cover 100km then it would use 12 litres of gas.
Are my calculations correct?

 Intermediate Member
 Posts: 1131
 Joined: Fri Jun 29, 2007 3:28 pm
 Location: Northants.
Re: Are my calculations correct?
Not far off, you may only lose 10%. Depends on the car and the system fitted. You may also need valve saver fluid at 50p per tank.
Re: Are my calculations correct?
Blimey, somebody thinking about it logically. I worked out that if petrol stays the same price (around £1.25 a litre even though I saw £1.29 tonight with the extra VAT), gas would need to get to £1.10 a litre before it costs me the same no matter which fuel I run on.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 ExPolice Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....
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'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 ExPolice Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....
Proud to be a member of the YCHJCYA2PDTHFH club.

 New member
 Posts: 172
 Joined: Sat Jun 06, 2009 12:37 pm
 Location: Taunton, Somerset
Re: Are my calculations correct?
If LPG MPG = 80% of Petrol MPG then;BigM wrote:Hi
My way of thinking is if I'm paying 72p per litre for gas, but loosing 20% efficiency compaired to running on petrol then I am running my car as if petrol was currently costing 86.4p per litre (as I'm having to use 20% more fuel to cover the same milage).
i.e 72+20%=86.4
Are my calculations right?
So to travel the same distance would use 20% more gas than petrol.
If my car used 10 litres of petrol to cover 100km then it would use 12 litres of gas.
LPG is 80%, to get to 100% would be:
LPG price: divided by 4 x 5, divide by 0.8 x 1.0 or x 1.25 (+25%)