Some advice about LPG conversion ...
How long is a piece of string? It all depends on how many miles you do and how long you intend to keep the car, also what sort of journies you do. Do not factor in a large increase in the second hand value of the car, it will definitely add less than the cost of the conversion. We had a Range Rover P38 with the 4.6 Rover lump in it that ran LPG. It took well over 2 years for a pay back on the investment, we saved a bundle after that so for us it was worth doing. If you are in London you don't have to pay the congestion charge on an LPG car but you do have to pay 10 quid a year to register it with TFL. Road fund is cheaper but again you have to change the registration status with DVLA to get that. The cost of fuel is obviously far lower but remember that most converted vehicles start on petrol and only switch over when the coolant temp reaches about 45 so for the part of the journey where your car is using most fuel - ie running cold and therefore rich, you will be burning petrol. The savings can be substantial but so can the conversion costs. Also you need to know that you can not take an LPG car on Euro Tunnel, it is forbidden. Can't think of anything else to add.
1/2er
1/2er
I have a LPG in my S-type 3.0. I do about 15-20k kilometers per year, petrol in Poland is quite expensive. LPG is about 50-55% cheaper.
Sir Arthur wrote that the LPG switches on the 45 degrees Celsius but it's not true
. In my car LPG switches at 30 degrees Celsius and it's not harmful for the engine and LPG parts.
When the weather is about 5-10 degrees Celsius my car switches after 300-500 meters!!! Even when is -10 deegres it's switch after max 1 kilometer
If you want I can take some photos of my instalation and send you
Sir Arthur wrote that the LPG switches on the 45 degrees Celsius but it's not true
. In my car LPG switches at 30 degrees Celsius and it's not harmful for the engine and LPG parts. When the weather is about 5-10 degrees Celsius my car switches after 300-500 meters!!! Even when is -10 deegres it's switch after max 1 kilometer

If you want I can take some photos of my instalation and send you
I agree MIKEY! HAHA! Thanks, I was only asking as I thought it would be a good idea in the future, maybe not for this car but others. PS: My mechanic says he can do it for Ł1500. So could start paying back after 12/18 months.
Did my STR last year, got sick of paying Ł25 a day to get to work!
This was a Ł2800 conversion which ive been mostly happy with. The issue was that its hard to get an evaporator that runs cleanly at 420HP, cheaper systems solution is to bodge 2 together (most kits are for <2.0litre engines).
Company that did it for me had done plenty of Range Rovers so had the experience with this engine.
Havent looked back, however I had a slight issue with fuel trims which the LPG makes worse and occasionally throws a check engine light. Ive subsequently identified a leaking injector on Cylinder 5 which is in the process of being replaced. Absolutely do not convert if you have less than perfect fuel trims - fix these first as Ive had to dismantle everything 3 times so hunting for vacuum leaks.
Makes me happy as its as economical to run as a diesel mondeo now
Last edited by dmdz; Apr 14, 2015 at 05:51 PM.
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Just seen you have the 3.0 duratec... I've seen the ST Mondeos (3.0l same engine) do well under a LPG kit, although the few conversion specialists I spoke with gave the the consensus that a flashlube kit is required as that engine suffers from dry valves. Make sure you go for someone who knows their stuff before spending that much cash on it!
I wouldn't do it!!!
I have had 4 cars LPG'd one of which was XJ8 3.2 which was fine.
Recently bought an x350 with V6 3.0L which had been converted but had some misfiring issues.
Thought it was either coils or vacum leak but ended up being low compression on 2 cylinders due to Valve seat reccession. when doing a valve clearance check there was no clearamce under the cam.
Needed 2 S/H heads and a fair few hours DIY to get running again.
I am sure it was caused by running on LPG and not having Valve Lube fitted.
Seems its a bit hit and miss with the Duratec engine for LPG it may be fine with a valve saver fitted but!!
I have had 4 cars LPG'd one of which was XJ8 3.2 which was fine.
Recently bought an x350 with V6 3.0L which had been converted but had some misfiring issues.
Thought it was either coils or vacum leak but ended up being low compression on 2 cylinders due to Valve seat reccession. when doing a valve clearance check there was no clearamce under the cam.
Needed 2 S/H heads and a fair few hours DIY to get running again.
I am sure it was caused by running on LPG and not having Valve Lube fitted.
Seems its a bit hit and miss with the Duratec engine for LPG it may be fine with a valve saver fitted but!!
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XJ XJ6 / XJ8 / XJR ( X350 & X358 )
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