LPG - MPG?? Range Rover 4.6 etc...
LPG - MPG?? Range Rover 4.6 etc...
Author
Discussion

Trellis

Original Poster:

590 posts

269 months

Friday 1st January 2010
quotequote all
Hi All

Can someone help me out?

What MPG can be expected from a 4.6 Vogue (for example) running on LPG?

I know LPG doesn't deliver the same miles as a gallon of petrol, but don't really know what this works out like for a Range Rover.

considering getting one for my better half and wondering if I could stomach the fuel bills..........

JW911

936 posts

225 months

Friday 1st January 2010
quotequote all
I have a 4.4V8 L322. I get 21 mpg on petrol or 17 mpg on LPG. I would imagine the 4.6 will be less but the proportion will be about the same.

Phil.

5,921 posts

280 months

Friday 1st January 2010
quotequote all
It's not a straight forward calculation because petrol will be used until the vehicle reaches 50 degrees C , so depends on how many cold starts or short journeys you make.

Roughly the cost of running on LPG is the cost of the normal petrol mpg but priced in diesel, halved i.e. (using round numbers) if you normally get 20mpg on petrol and the cost of diesel is £6 per gallon then the fuel cost on LPG will be equivalent to 40mpg at £6 per gallon.

If it's already been converted to LPG then get the system checked out by professionals before buying - the systems are often incorrectly fitted or just worn out if they haven't been maintained properly.

If you are having the LPG system fitted then be very careful who you select to fit it - avoid the Google route! Speak to owners of vehicles of the same make that they have converted before you selecting!

Best of luck...

Phil.

5,921 posts

280 months

Friday 1st January 2010
quotequote all
JW911 said:
I have a 4.4V8 L322. I get 21 mpg on petrol or 17 mpg on LPG. I would imagine the 4.6 will be less but the proportion will be about the same.
I have a L322 4.2V8 S/C converted to LPG. I'd be interested to know what LPG set up you went for. Any hitches?


JW911

936 posts

225 months

Friday 1st January 2010
quotequote all
Prins multi-point. You don't even know it's there. The only issues were a whistling gas regulator (an adjustment soon cured it) and the fact that I now consider 56.9p/l to be expensive!

Triple7

4,015 posts

267 months

Saturday 2nd January 2010
quotequote all
My 4.0 P38 did late teens in petrol guise. An LPG would do less. Agree these things cost a fortune to run as stop/start cars.

Triple7

4,015 posts

267 months

Saturday 2nd January 2010
quotequote all
My 4.0 P38 did late teens in petrol guise. An LPG would do less. Agree these things cost a fortune to run as stop/start cars.

agent006

12,058 posts

294 months

Saturday 2nd January 2010
quotequote all
The better the LPG system (and the better set up it is), the smaller the difference in MPG. My old 4.6 did 17mpg on LPG. Didn't run it that often on petrol but when i did there wasn't a noticeable difference (went from 17.something to 17.somethingelse).

Trellis

Original Poster:

590 posts

269 months

Saturday 2nd January 2010
quotequote all
Thanks for all your comments guys - given the amount of stop / start, round town driving she does, I doubt LPG is going to be as sensible as a diesel!


kVA

2,460 posts

235 months

Saturday 2nd January 2010
quotequote all
Trellis said:
Thanks for all your comments guys - given the amount of stop / start, round town driving she does, I doubt LPG is going to be as sensible as a diesel!
If you're just doing stop / start around town, does this mean it will be doing low mileage?

If so, you will get much more car for your money with a straightforward petrol car than a diesel. I don't understand this obsession we have with mpg in the UK: Unless you are doing 20-30,000 miles per year, just spend £2,000 less on the car (e.g. buying a petrol rather than a diesel) and enjoy the performance, refinement, and all the toys (petrol versions are nearly always higher spec cars).

I ran a Supercharged RRS for a while - paid £5,000 less than the cheapest TDV8 available at the time - that's a shed load of V-Power! Worth every penny for the grin factor alone.

Edited by kVA on Saturday 2nd January 19:53

agent006

12,058 posts

294 months

Saturday 2nd January 2010
quotequote all
Trellis said:
I doubt LPG is going to be as sensible as a diesel!
Depends if you buy one already converted or not. Given that (when i was buying, at least) there doesn't seem to be a premium to pay for buying an LPG converted car, it made perfect sense to run LPG.

Don't expect the diesel to be a paragon of economy though. From what i've read, both P38 and L322 diesels will deliver barely 20mpg round town.

Phil.

5,921 posts

280 months

Saturday 2nd January 2010
quotequote all
kVA said:
Trellis said:
Thanks for all your comments guys - given the amount of stop / start, round town driving she does, I doubt LPG is going to be as sensible as a diesel!
If you're just doing stop / start around town, does this mean it will be doing low mileage?

If so, you will get much more car for your money with a straightforward petrol car than a diesel. I don't understand this obsession we have with mpg in the UK: Unless you are doing 20-30,000 miles per year, just spend £2,000 less on the car (e.g. buying a petrol rather than a diesel) and enjoy the performance, refinement, and all the toys (petrol versions are nearly always higher spec cars).

I ran a Supercharged RRS for a while - paid £5,000 less than the cheapest TDV8 available at the time - that's a shed load of V-Power! Worth every penny for the grin factor alone.

Edited by kVA on Saturday 2nd January 19:53
Agree with some of the above but to add....

1. Compare the cost of depreciation over the period of ownership/miles NOT just the purchase price for the diesel/petrol. Then add in the cost of fuel at diesel/petrol prices and their relative MPG.

2. If you're not doing 20k+ miles per year then stay away from LPG unless its already been fitted (and have it checked out professionally before buying) otherwise the cost saving of fitting LPG will not be sufficient.

3. By the time you finished (1) and (2) the maths still won't add up so go out and buy what you want and enjoy a brilliant vehicle for a few years!


kVA

2,460 posts

235 months

Saturday 2nd January 2010
quotequote all
Phil. said:
1. Compare the cost of depreciation over the period of ownership/miles NOT just the purchase price for the diesel/petrol. Then add in the cost of fuel at diesel/petrol prices and their relative MPG.
I agree if you are talking about new cars, but as soon as any car is a couple of years old the rate of depreciation between petrol and diesel is almost identical - and you get a better car for the same money with a petrol.

Personally, I wouldn't buy an LPG car anyway... You can't take it on Eurotunnel (which I use regularly) and this...


Phil.

5,921 posts

280 months

Saturday 2nd January 2010
quotequote all
kVA said:
Personally, I wouldn't buy an LPG car anyway... You can't take it on Eurotunnel (which I use regularly) and this...
As I have said above - if you buy a vehicle fitted with LPG then get it checked by a professional.

But what does your photographic evidence of a LR on fire have to do with LPG? What facts do you have to support your LPG scaremongering?

agent006

12,058 posts

294 months

Saturday 2nd January 2010
quotequote all
Phil. said:
As I have said above - if you buy a vehicle fitted with LPG then get it checked by a professional.
This is the problem with LPG. People fit it or buy something with it fitted, ignore it for tens of thousands of miles and are then surprised when it goes wrong/explodes. An equally neglected petrol system will have the same amount of problems, except it won't because that's covered by the MOT.

kVA

2,460 posts

235 months

Saturday 2nd January 2010
quotequote all
Phil. said:
kVA said:
Personally, I wouldn't buy an LPG car anyway... You can't take it on Eurotunnel (which I use regularly) and this...
As I have said above - if you buy a vehicle fitted with LPG then get it checked by a professional.

But what does your photographic evidence of a LR on fire have to do with LPG? What facts do you have to support your LPG scaremongering?
The fact that I sat for 2.5 hours on the M40 on a Bank Holiday waiting for the fire crew to declare that there was no longer an explosion risk from the LPG tank in the Range Rover concerned!

Here's some more people that weren't too pleased about LPG cars that day either... wink


kVA

2,460 posts

235 months

Saturday 2nd January 2010
quotequote all
Quinny said:
kVA said:
The fact that I sat for 2.5 hours on the M40 on a Bank Holiday waiting for the fire crew to declare that there was no longer an explosion risk from the LPG tank in the Range Rover concerned!

Here's some more people that weren't too pleased about LPG cars that day either... wink

What a load of bks.... LPG Fires in converted cars are far rarer than petrol fires in non convertedrolleyes

fk me, a few years ago you couldn't travel on any motorway wiyhout seeing a bloody wagon on fire, or the remains of one.....Flammable stuff that Diesel
Wish you had been there - you could have told the Fire Chief, that I was talking to, yourself rolleyes Unfortunately I was the first vehicle to be stopped when they closed it, so naturally, I asked why...

Just one question - if it wasn't an explosion risk, why do you think they closed BOTH lanes of the Motorway until the wreck had cooled down?

Phil.

5,921 posts

280 months

Saturday 2nd January 2010
quotequote all
kVA said:
The fact that I sat for 2.5 hours on the M40 on a Bank Holiday waiting for the fire crew to declare that there was no longer an explosion risk from the LPG tank in the Range Rover concerned!

Here's some more people that weren't too pleased about LPG cars that day either... wink
So it was a one off you happend to witness. Was it the petrol or the LPG that caused the fire? If the LPG had been the cause the LPG tank would not have been a concern for the fire crew it would have blown up! It was obviously a petrol fire and how many do we see of those each day? It seems that the LPG tank didn't go up despite the fire which is plus rather than a negative for the safety of LPG.

Why the need to scaremonger? Facts please rather than complete twaddle.


Phil.

5,921 posts

280 months

Saturday 2nd January 2010
quotequote all
Quinny said:
kVA said:
Just one question - if it wasn't an explosion risk, why do you think they closed BOTH lanes of the Motorway until the wreck had cooled down?
I've no idea.... Perhaps you should have told the fire chief that the risk of an explosion from an LPG fire is far lower than that of a petrol fire.....If you knew what you were on about, perhaps you could have saved all that hanging aroundsmile

What about fire risks?

An LPG system already addresses most fire risks by ensuring that no fuel can escape, preventing it from making any impact induced fire more severe.

But there is another problem to consider. What if the vehicle is burning so badly that the fuel tank is heated by the flames?

Again, a metal Petrol or Diesel tank affords little protection here, and a plastic tank will actually melt. Only moderate amounts of heating from the outside will result in a catastrophic explosion, spreading burning liquid fuel all around the scene. (Pound for pound, liquid Petrol has an explosive potential approaching that of Dynamite.)

An LPG tank, however, is designed to slowly release its contents via a safety valve (much the same as those fitted to compressor tanks or steam engine boilers). If the pressure within the tank becomes greater than a preset level, the valve will 'blow off'. The preset level is much less than the pressure that would cause the tank to explode. Admittedly, the venting of gas will probably result in a jet of flame, but at least some control of its direction is afforded and an explosion is avoided.


Conclusion

Considering all of the factors above, an LPG fuel system is quite a lot safer than most Petrol or Diesel systems.
My research concluded much the same before I decided to sit my kids in front of a 90lt LPG tank. I also included impact analysis in my research and the LPG tank in a RR should be sited to minimise this risk. It is in mine!


Edited by Phil. on Saturday 2nd January 23:57

kVA

2,460 posts

235 months

Sunday 3rd January 2010
quotequote all
Excuse me, but I just expressed a personal opinion that I wouldn't buy an LPG car of any description...

As for telling a Fire Chief his job (when they clearly considered the risk sufficiently serious to close both lanes of the M40 for over 2 hours and call 5 fire tenders to an incident involving just one vehicle) are you having a laugh?

The OP is clearly trying to make a decision about LPG and I posted some information that I would want to be aware of if I was making the decision.

In particular, if the risk is really so low, why are all LPG vehicles banned from Eurotunnel?



In my experience, people who become abusive and personal, when defending their own choices, usually have some doubts themselves. Your choice, but I wouldn't sit my dogs next to an LPG tank, let alone kids.