LPG vs Diesel

[silent k]

Am I missing something with LPG as it seems to make a lot of sense?

I've being looking at getting something like an Audi A6 diesel, as I'm probably going to be doing a lot more miles in the next 12 months (around 25k). This would do around 40mpg, but conversely I could get an A6 2.7 Twin Turbo with loads more power, and convert it to LPG, now this would do around 20 mpg (about 23-24 on petrol) but LPG costs about half the amount so would work out the same.

So have I missed something? I could be driving a 2.7 twin turbo instead of a 2.0 diesel for the same running costs? I appreciate the cost of conversion is around 1,500 but I'd be willing to pay that as a one off to have the 2.7 twin turbo!

[kambites]

The only real problem is the fact you lose half your boot. Of course there's also no guaranty that the government wont put up the tax on LPG. I think cars are a bit less efficient on LPG than petrol too, although I could be wrong there.

[james_tigerwoods]

That'll work right up until LPG is taxed as much as normal fuel once it's popularity picks up. Economy using LPG is not much better than petrol.

If LPG is taxed the same as petrol, it will wipe out any running cost benefits....

[Kieran XJR]

I seem to remember reading somewhere that the performance is actually better when running on LPG. Any know if that's true or not?

[silent k]

The boot space thing isn't too much of a problem, as it's only the dog who goes in the boot and he doesn't complain much

The tax thing I suppose is the main issue, I wonder how likely it is that it'll change as LPG doesn't seem to be pushed as much as it was before. If the tax rate stays the same for the next 3 years or so, then that's good enough really.

Edit : Found this http://www.greenfuel.org.uk/lpg/government it basically says the government will give 3 years notice of any change in duty on LPG

Edited by silent k on Thursday 28th February 15:33

[dunkie]

Kieran XJR said:

I seem to remember reading somewhere that the performance is actually better when running on LPG. Any know if that's true or not?

I read this also as it burns cleaner, but this is off the top of my head (and its been 10 years since i did chemistry at uni)

I am still pondering getting a Mustang GT and LPG'ing it, but the goverment are so arsey about fuel tax etc I really dont want to pay a fortune for LPG if they end up increasing the tax big time

Still gonna ponder away though

[Crusoe]

add on the losses you would have selling the car after an lpg conversion the derv option is the one to go down or get a smaller petrol engine or a cheap second hand S8 and go in comfort spending the extra on fuel

[Kieran XJR]

dunkie said:

Kieran XJR said:

I seem to remember reading somewhere that the performance is actually better when running on LPG. Any know if that's true or not?

I read this also as it burns cleaner, but this is off the top of my head (and its been 10 years since i did chemistry at uni)

I am still pondering getting a Mustang GT and LPG'ing it, but the goverment are so arsey about fuel tax etc I really dont want to pay a fortune for LPG if they end up increasing the tax big time

Still gonna ponder away though

Maybe you can justify it's worth as a performance mod alone?

Edited by Kieran XJR on Thursday 28th February 15:49

[215cu]

Government can't tax LPG, duty is set by the EU in a bid to get more petrol cars converted to it (as it is a very popular conversion in Europe-land).

Have thought about the LPG angle for a MG ZT260 which has been done several times and the car can take a hefty 80L (64L in reality) tank in the boot giving a reasonable LPG range of about 240 miles.

As for power v petrol, they say it's about 85% that of regular leaded (95RON). However it's another item to have serviced. As long as you do more than about 40,000 miles in the car, it'll pay for itself. There's a small residual on the LPG conversion when it comes to sell too.

[silent k]

It definitely seems a possibility then, if I work on having the car for 3 years/ 75,000 miles.

It just doesn't seem like much of a comparison - 2.7 Twin turbo vs 2.0 tdi!

[biglepton]

I ran a Discovery 300TDi alongside a similar age Discovery 4.0 V8 auto on LPG.

The TDi averaged 29mpg and the V8 16mpg but a litre of lpg cost me 38% of the cost of a litre of diesel, so the V8 cost less per mile to fuel than the diesel. Needless to say the V8 auto (complete with s/s sports exhaust system) was by far the nicest to drive. Petrol engines only run less well on lpg if they are not set up properly. Lpg is 114 octane so if you advance your ignition to take advantage of that fact, it will drive better than a petrol. Mine had a small automatic ignition advance box fitted which advanced the ignition a lot when it switched to lpg and it then produced noticeably more power and torque than on petrol whilst returning the same mpg and having much better throttle response and willingness to rev past 5k. The only downside with lpg can be a reduced range if the lpg tank is small, but with the Disco it had two 36l tanks underslung in the chassis recess' and the petrol tank replaced with a 50l (IIRC) tank and a small auxilliary petrol of a couple of gallons, so range was about 400 miles.

Diesel is OK, but a nice big six or eight cylinder petrol/lpg engine for the same MPG cost equivalent is much nicer!

[richyb]

I've though about this before and I'm not sure about it all. From what I've read LPG is supposed to give about 10% less mpg than the standard petrol. Just my basic maths but that means your average petrol saloon probably gets about 30 so 27 on lpg. So a gallon of LPG would cost you £2.25 (4.5 * 50p la litre), so 8.3p a mile. The average diesel saloon gets about 45mpg and one gallon costs £4.91 (4.5* 109p) so works out just about 11p a mile. I know thats completely basic but it would seem to be cheaper per mile. How much does conversion cost you? I am guessing about £1500ish. Agree that there is a potential to have LPG jump up in price if the taxation changes but to be honest diesel keeps going up anyways. Just my take on it all.

[Crusoe]

only conversion i've helped with was a 3.3lr alpina bmw, was getting 24mpg on petrol and only 14mpg on lpg. Was worth it just for the increased range from the twin tanks but takes up a lot of boot room and there aren't many garages to fill up at.

[funinthesun]

had an audi a6 4.2 converted to LPg for a couple of years, never missed a beat as far as the lpg system was concernbed althoug did find it didnt work in very cold temperatures ( less than minus 15)

only issue i had was size of the LPG tank, as it sat in the spare wheel well, and the fact that you did have to plan journeys a little to make sure you passed a station selling the stuff...averaged about 22mpg on lpg, but then thats about 45mpg for the same £ in petrol...

[kneilson]

I bought a S80 as something to rack up the miles in for work, it came from the factory as a Bi-Fuel model. It has been great, it's MUCH cheaper running on LPG, it works out at the equivalent of 48mpg at current fuel costs....not bad for a comfy big barge that's not exactly light!

[Kev 735V8]

Interesting debate. I was looking for advice on Ford Mustangs on LPG and saw your thread.

All I can say is:
BMW735 V8 owner 2000 X
acquired 2006 52k
now done 106k
lpg conversion in sept 06 by Go-lpg.co.uk
lpg tank is 90L torpedo in boot
lost one third of boot space but still loads of room
25 mpg on petrol
lpg mpg is 23 if careful and 18 if gunned
do not buy your gas from bp/shell etc - too exp.
buy your gas from countrywide - 44p
http://www.countrywidefarmers.co.uk/pws/Content.ic...
gas conversion cost £2,000
i drive 25,000 pa
paid for itself in 9 months
be careful - anything non-lpg wrong with the car will be worse with lpg as the car needs to be set up right to run ok on gas
once the gas conversion settled down performance has been good and not noticeibly different to petrol.
would definately get another lpg car again.
ford mustang 07 on gt maybe next who knows.
happy to field direct questions as i wont be logging on to this site very often.
there are plenty of places to buy lpg and not have to pay bp prices - the lpga sells a book with a list of lpg outlets in the uk and they are everywhere.
countrywide are the best because they put their lpg tanks in car parks with digital code access and are unmanned so you can fill up 24 hrs a day.
car averages 22mpg on lpg / 44p/107p = equivalent of 54mpg - not bad for a 7 series with cream leather and all the trimmings.
just make sure you get it converted by a lpga assocn member who is local to you as you will get teething problems but if you stick at it then its a no-brainer.
even compared to a diesel saloon doing 40mpg I am saving £900 in cash a year or £1500 gross taxable income.

Good luck guys.

Kev 735V8 (Worcester)

[DippedHeadlights]

Funny, just replied to the "looking for big estate" topic on this when everyone else was suggesting diesel.
I'm a big fan of LPG, been using it in my XC70 for 18 months. Saved a fortune, really gives you the best of both, performance of a petrol and economy of a diesel - in fact better than that, the diesel auto XC70 only does 35ish to the gallon and feels sluggish even with 185hp. The petrol turbo is over 200hp and feels alive - and I get 25mpg running on lpg at about 50p a litre.

DH

[DucatiGary]

215cu said:

As for power v petrol, they say it's about 85% that of regular leaded (95RON).

they

i love this they, they always know everything, dont they.

ohh and on this one im calling bks, never noticed any loss of power in mine, as for service its 60 quid "if" "they" need to replace the filters, 20 quid if not.

its not a oil change or nothing, just a check to see everything is working, 20 min job.

[ironictwist]

LPG E36 328 = Same amount per week to run as my 1.6 Astra running on petrol when doing 300+ miles a week to work & back. Then again, my system is dated & just generally crap. With a nice new system you'll notice some real gains I think. Give it a go

[Hooli]

DucatiGary said:

215cu said:

As for power v petrol, they say it's about 85% that of regular leaded (95RON).

they

i love this they, they always know everything, dont they.

ohh and on this one im calling bks, never noticed any loss of power in mine, as for service its 60 quid "if" "they" need to replace the filters, 20 quid if not.

its not a oil change or nothing, just a check to see everything is working, 20 min job.

i think the energy value of LPG is lower, thats why it gets a lower MPG - you burn more for the same power output.

unless its changed in the last few years there was a goverment scheme that paid a large %age of the conversion cost if the car was under 3 years (i think) old.