Discussion
Hi all,
Can anyone help, I am considering buying an Audi A8, either the 4.2 FSI or the 4.2 TDI 40-50k on the clock 2007/8 MY. I do about 18-20,000 miles a year and with the petrol doing about 24mpg and the diesel only returning 29mpg, and with the petrol model circa £3k cheaper I am considering converting to LPG with a high end system (£2600) and benefiting from the cheaper fuel (diesel is 4p more than petrol and LPG is 59p a litre).
I have heard horror stories about engine issues, although I understand if you get the self lubing system this combats most valve issues and understand there will be some drawbacks but on the surface it appears a no brainer.
I tend to keep cars a while (120-150k) so would be looking to run it for about 5 years.
Any thoughts or recommendations?
Can anyone help, I am considering buying an Audi A8, either the 4.2 FSI or the 4.2 TDI 40-50k on the clock 2007/8 MY. I do about 18-20,000 miles a year and with the petrol doing about 24mpg and the diesel only returning 29mpg, and with the petrol model circa £3k cheaper I am considering converting to LPG with a high end system (£2600) and benefiting from the cheaper fuel (diesel is 4p more than petrol and LPG is 59p a litre).
I have heard horror stories about engine issues, although I understand if you get the self lubing system this combats most valve issues and understand there will be some drawbacks but on the surface it appears a no brainer.
I tend to keep cars a while (120-150k) so would be looking to run it for about 5 years.
Any thoughts or recommendations?
I'm not aware of any lubrication issues with LPG - petrol has virtually no lubricating properties anyway. I know plenty of people who've run all sorts of petrol engines for hundreds of thousands of miles on LPG and as far as I know none of them have ever had a problem with the engine caused by the LPG.
sinizter said:
FSI cannot be fully converted to LPG IIRC, it will still use upto 25% petrol even after being warmed up and switched over to LPG.
This still works out substantially cheaper than running the TDI, and I note your comments about the lubricating qualities of petrol, however I understand that LPG is injected into the cylinders as a "dry" gas and contains no friction inhibitors or lubricating added agents unlike petrol. This can lead to excessive valve seat wear in high performance, and indeed may 'cook' engines. However fitting a 'FlashLube' system at the same time as the conversion will extend valve-seat life dramatically or replacing the valves/ seats with hardened ones can combat this issue.kambites said:
sinizter said:
FSI cannot be fully converted to LPG IIRC, it will still use upto 25% petrol even after being warmed up and switched over to LPG.
That's still a fair fuel saving, though. 
Out of interest, why? Does something overheat?
Any lubrication issues can be handled by installing a Flashlube system along with the LPG install.
All this info is from when I was looking into buying a new car with an idea of converting - not personal experience. Things may have changed now - although this was only about 6-9 months ago.
The numbers don't really stack up for LPG these days...
If a decent conversion costs £2500, and
LPG costs 75p/litre (£3.41/gallon)
Petrol costs 1.40/litre (£6.37/gallon)
The saving by using LPG is £2.96/gallon
You would have to use 845 gallons before you break even which is over 21,000 miles*
(* at 25mpg, which is probably the level you get from a car you would consider getting an LPG conversion performed on)
In fact, the breakeven point is probably even higher than that, as I understand that LPG isn't quite as efficient as petrol, litre for litre.
If a decent conversion costs £2500, and
LPG costs 75p/litre (£3.41/gallon)
Petrol costs 1.40/litre (£6.37/gallon)
The saving by using LPG is £2.96/gallon
You would have to use 845 gallons before you break even which is over 21,000 miles*
(* at 25mpg, which is probably the level you get from a car you would consider getting an LPG conversion performed on)
In fact, the breakeven point is probably even higher than that, as I understand that LPG isn't quite as efficient as petrol, litre for litre.
monthefish said:
The numbers don't really stack up for LPG these days...
If a decent conversion costs £2500, and
LPG costs 75p/litre (£3.41/gallon)
Petrol costs 1.40/litre (£6.37/gallon)
The saving by using LPG is £2.96/gallon
You would have to use 845 gallons before you break even which is over 21,000 miles*
(* at 25mpg, which is probably the level you get from a car you would consider getting an LPG conversion performed on)
In fact, the breakeven point is probably even higher than that, as I understand that LPG isn't quite as efficient as petrol, litre for litre.
Buy it already converted, then the savings start immediately.If a decent conversion costs £2500, and
LPG costs 75p/litre (£3.41/gallon)
Petrol costs 1.40/litre (£6.37/gallon)
The saving by using LPG is £2.96/gallon
You would have to use 845 gallons before you break even which is over 21,000 miles*
(* at 25mpg, which is probably the level you get from a car you would consider getting an LPG conversion performed on)
In fact, the breakeven point is probably even higher than that, as I understand that LPG isn't quite as efficient as petrol, litre for litre.
monthefish said:
The numbers don't really stack up for LPG these days...
If a decent conversion costs £2500, and
LPG costs 75p/litre (£3.41/gallon)
Petrol costs 1.40/litre (£6.37/gallon)
The saving by using LPG is £2.96/gallon
You would have to use 845 gallons before you break even which is over 21,000 miles*
(* at 25mpg, which is probably the level you get from a car you would consider getting an LPG conversion performed on)
In fact, the breakeven point is probably even higher than that, as I understand that LPG isn't quite as efficient as petrol, litre for litre.
Even comparing to diesel using your figures, after about a year (just over) I am still quids in leaving the next few years as half price motoring.If a decent conversion costs £2500, and
LPG costs 75p/litre (£3.41/gallon)
Petrol costs 1.40/litre (£6.37/gallon)
The saving by using LPG is £2.96/gallon
You would have to use 845 gallons before you break even which is over 21,000 miles*
(* at 25mpg, which is probably the level you get from a car you would consider getting an LPG conversion performed on)
In fact, the breakeven point is probably even higher than that, as I understand that LPG isn't quite as efficient as petrol, litre for litre.
Does anyone have any views on whether duty is going to be increased on LPG as this would obviously nail a positive argument?
GrandGinge said:
Even comparing to diesel using your figures, after about a year (just over) I am still quids in leaving the next few years as half price motoring.
Does anyone have any views on whether duty is going to be increased on LPG as this would obviously nail a positive argument?
I believe the (labour) government put a bill through parliament meaning that any government has to give a certain amount of notice (five years maybe?) before closing the gap between petrol and LPG duty. Something like that, anyway. Does anyone have any views on whether duty is going to be increased on LPG as this would obviously nail a positive argument?
LPG duty will go up soon....but only in line with petrol/diesel, so when 3p goes on petrol/diesel in January it will go on LPG too.
Because of the much smaller tax component, LPG tracks oil prices far more than Petrol/Diesel so if oil goes up the differential will not look so good but if oil goes down LPG will head back towards the 50p/litre mark whilst the other will still be £1.20
Because of the much smaller tax component, LPG tracks oil prices far more than Petrol/Diesel so if oil goes up the differential will not look so good but if oil goes down LPG will head back towards the 50p/litre mark whilst the other will still be £1.20
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