Let's discuss LPG on the V12 (again)

Hi there.

It looks as though LPG was last talked about on here over 15 years ago… so how about an updated discussion on it… (unless you’re all avoiding the topic for a particular reason?)

With this electric/green agenda unfolding everywhere and that our beloved petrol is not only getting expensive but much harder to find good quality low-ethanol stuff, LPG as a dual fuel maybe should be a consideration?

Two things:

1.) The “go-lpg.co.uk” website … there’s a lot of info on there but I get the hunch that it was last updated about 15-20 years ago … are these guys still doing V12 LPG conversions in 2021?

2.) I seen a youtube video recently from a Polish LPG company that claim they have successfully converted a Jaguar XJS V12 with LPG:

It’s obviously in Polish, but it seem legitimate enough … what do you think?

I’m really intrigued about going dual fuel on my XJS but need some updated info on the whole LPG conversion as I know it isn’t trivial, nor cheap. Anyone here who has a successful conversion?

Best regards,

@MarekH is your go-to guy!


Dear Owen,
if you use the search function and also look at the “old website” photo albums, then you’ll find plenty of details of my v12 running dual fuel, lpg and petrol.
kind regards


Hi there Marek. I’m glad to hear that LPG conversions are still supported today. btw, my “old website” remark wasn’t taking the piss. :wink: … it was more to do with seeing if this conversion idea was still supported to this day. I guess Google search results didn’t bring up everything.

Anyway, my main question is where do I start with all of this? What would you recommend for an '84 V12 HE XJS? (What I have).

Kind regards,

Is a 1984 xjs worth spending money on? You have to decide how much money you want to spend and the only collectible v12 Jaguar is the etype, so it very marginal as to whether significant expenditure is worth making. At some point, the xjs be as desirable, so will hopefully justify the expense of replacing the Lucas fuel injection and at that point, it becomes economical to tack on an lpg conversion.

For the etype was an easier decision, as it remains a valuable car whether it has carburettors, fuel injection, or a dual fuel setup. In my case, I fuel injected the car at an expense of about GBP1500 to 1700 and the lpg setup was the same amount again. That sort of outlay is proportionately a higher amount for an xjs to swallow and a complete non-starter for an xj12.

I wouldn’t consider a piggy-back system even though you already have fuel injection. I would look to replace the 37 year old Lucas components with a modern ECU that is capable of handling multiple maps and has control of ignition and all peripherals aswell.

A properly executed lpg conversion should always have second hand value in the UK so long as the differential pricing exists between petrol and lpg, so the big decision is how much you want spend on a modern fuel injection system by reference to the car’s overall value. If your current fuel injection setup is now almost life expired, but the bodywork isn’t and you want to keep the car long term, then the decision becomes easier.

I run a Megasquirt v3.0 with sequential fueling and wasted spark ignition.

kind regards


When I bought my 75 XJ12C it was converted to run strictly on LPG with two tanks and two throttle bodies. I converted it back to gasoline (and it never again). If anyone wants the LPG kit, let me know. I kept all the stuff and would be happy to sell it.


one of the interest could be if running LPG would be a way to pass the emission free zones ?

on practical aspects, you’ll need a place to put the LPG tank (if you keep the dual fuel),

as the V12 is quite thirsty, mileage could be limited as LPG is about 15% less, according to

It depends on the jurisdiction. Over here (UK), there are concessions for LPG cars in some of the low emission zones.

Torroidal LPG tanks typically replace the spare wheel. (You can fit a spare wheel in the etype boot and the xj12 has more space than an etype.)

One concern is that electric cars are killing LPG. The reason for this is that much of the uptake of LPG was from taxis and these have now converted to electric, rather than LPG. Accordingly, the number of filling stations has dropped and that means it is a less attractive option to fit LPG. The price differential between petrol and LPG has also narrowed from ~50% to 33%. None of this is welcome news.

It is still cheaper than petrol and a higher octane fuel. Mileage is only slightly lower and is still more than offset by the price differential.

kind regards

we have 2 Volvo 940 1 is turbo one is not
also have Austin A35 with mg midget engine
Volvo Amazon
all run on lpg
and over the next few months
will do XJ6 series 2 I think I can get 100 litre in the jag
and keep its twin petrol tanks
if you buy LPG in bulk 2000 lts its 35 P litre
cos it is just propane

Hmmm…this post is almost two years old, but I’d consider the LPG kit. Let’s talk if you still have it: purpleporsche@icloud.com