60mpg in a S500

[jaymanek]

The best is when people who do very low mileages go and convert their old cars just for the warm fuzzy feeling of getting 60 mpg (yeh right)...

With most average cars, it takes around 15-20K miles to recoup the initial investment, only after this do you really start saving... so someone doing 5K miles will take 3-4 years... by this time fuel costs may have risen, the government may decide to change the duty on LPG or your car may have collapsed and died...

And then it comes to resale value, many cars are actually worth less with these systems on, especially prestige cars like Mercedes.

Its a great alternative but only for high mileage users who will get their investment back in a few months.

 

[flango]

I was not making such assumptions, perhaps you were making some assumptions of my and others knowledge on this? It is not about scoring points jbut about clarity.

I am aware of the newer systems having seperate ECU's etc as I have looked in to this in some detail. I just chose not to include that information in my replies as the point I wanted to make was in reference to the specific chemistry and physics of LPG vs petrol and to dispell the myth that LPG cars travel further per gallon / litre etc when clearly they cannot when in fact what LPG gives is a lower cost per mile and a cleaner burn with a lower pollution burden.

This difference in fuel burnt per mile is perhaps shown more clearly when an average LPG tank of 80 litres would give you a lower range in miles etc than an equivalent size of petrol tank plus all LPG tanks have a capacity that is approximately 20% lower than maximum due to space required for expansion.

It is clear that the adoption of specific mapping etc will make LPG cars more reliable, drivable and fuel efficient and yes it is much cheaper per mile in terms of cost of fuel burned

I wasn't having a go or points scoring, in fact my post was not directed at your comments at all, as I agree with everything you say and it is always good to get clarity on things. I was merely trying to point out to others reading the thread that LPG systems have taken a massive step change and are now much better than they have ever been

 

[flango]

The best is when people who do very low mileages go and convert their old cars just for the warm fuzzy feeling of getting 60 mpg (yeh right)...

With most average cars, it takes around 15-20K miles to recoup the initial investment, only after this do you really start saving... so someone doing 5K miles will take 3-4 years... by this time fuel costs may have risen, the government may decide to change the duty on LPG or your car may have collapsed and died...

And then it comes to resale value, many cars are actually worth less with these systems on, especially prestige cars like Mercedes.

Its a great alternative but only for high mileage users who will get their investment back in a few months.

Totally agree and would never consider it on any of our other cars as they don't do enough miles, but I am seriously considering it for my next daily driver as I do 30k + miles per year so reckon my recoup will only be 6 months after which I could get half price motoring. I never even considered this option until we fitted our Discovery with LPG and that really amazed me and opened my eyes.

 

[DSM10000]

Hi, I was not directing my comments negatively at you either! Just trying to tidy up my points for others dropping in on the thread.

As a research scientist it is my nature to be scientific at times Ask my other half as she often says "you can explain things in small words as well you know?"

The other potentially important thing for people to be aware of if considering converting is that LPG fuelled vehicles are prohibited from using Eurostar and some ferry operators are not keen on them.

 

[Melk63]

All very useful information. I wonder if the economics for high miles are so good, why don't company fleet operators convert their fleet? Also, are there limits to what engines can be converted? v12 biturbo a candidate? What is the conversion cost? Thanks. Mel.

 

[kth286]

there are also a couple of additional benefits with LPG.


Apart from a higher octane, it is also a gas as it enters the cylinders and not a liquid like petrol, so the oil is not affected by bore wash, which means less engine wear.

Also because gas is cleaner the engine oil will not degrade as quickly, and can realistically be left much longer before changes, hence saving more money.

Also of course gas is much friendlier from an emissions point of view, so you are doing your bit extra for the planet.

 

[Borys]

All very useful information. I wonder if the economics for high miles are so good, why don't company fleet operators convert their fleet? Also, are there limits to what engines can be converted? v12 biturbo a candidate? What is the conversion cost? Thanks. Mel.

Convert a car in Uk is quite expensive.Newer the car more complicated it is. My friend is gasoholic but done a mistake and bought audi a6 with fsi engine-none of the known to me garages want to take on the project.You need to check with the installer.
I paid for my install 800quid (120liter tank)but was done in Poland once on holiday.Garages charges over there are 5£-10£ per hour for labour !!!!!!

 

[e320cdiowner]

I read someway that lpg conversion burns hotter than the petrol fuel( 10 years ago aprox ) and hence some damage to the engine . Is this still true now?

 

[Deleted member 6183]

Any idea how much conversion costs in the uk? I cover the miles and could either convert my own or get a cheap luxobarge and convert it.

 

[flango]

Any idea how much conversion costs in the uk? I cover the miles and could either convert my own or get a cheap luxobarge and convert it.

For the top spec Gen4 systems fully fitted and registered with DVLA prices as follows

3-4 cylinder £975
6 cylinder £1150
8 cylinder £1350

This is for normally aspirated engines for turbo or supercharged engines price is slightly higher and some engines are known not to be LPG friendly so the installers won't touch them but it really is a minority of obscure stuff.

 

[Deleted member 37751]

For the top spec Gen4 systems fully fitted and registered with DVLA prices as follows

3-4 cylinder £975
6 cylinder £1150
8 cylinder £1350

This is for normally aspirated engines for turbo or supercharged engines price is slightly higher and some engines are known not to be LPG friendly so the installers won't touch them but it really is a minority of obscure stuff.

That's a lot less than I would have imagined, I might be able to justify an LPG E63 for my next car....

 

[flango]

Also when you register your car with the DVLA and change it to a dual fuel vehicle you pay less road tax and are exempt from the London congestion charge

 

[Deleted member 6183]

This is adding up for me. Even converting my 5 series could make sense. I do at least 3000 miles a month, petrol 3.0, 6 cyl. Currently seeing 32mpg but only runs right on shell v power. Employer pays 28p/mile fuel only.

Wonder what resale is like?

 

[flango]

This is adding up for me. Even converting my 5 series could make sense. I do at least 3000 miles a month, petrol 3.0, 6 cyl. Currently seeing 32mpg but only runs right on shell v power. Employer pays 28p/mile fuel only.

Wonder what resale is like?

Resale is patchy, as Jay says it actually devalues MB but is seen as a benefit and gives a slight premium on resale on others. I was told the best way before resale is to take off the LPG kit and no one is the wiser the sell the LPG Kit separate apparently there is a good market for second hand LPG kits.

I was going to get another diesel to replace the Volvo because of my high mileage the volvo averages around 60mpg, however if I now get a decent petrol fit LPG I could have a car that gives close to 70 mpg equivalent :bannana:

 

[Dieselman]

Result normal run 30mpg but as gas is half the price we got 60mpg.
For 50£ in a town will do 250 miles.

At 20p per mile it's cheaper to drive diesel.

 

[Dieselman]

This is adding up for me. Even converting my 5 series could make sense. I do at least 3000 miles a month, petrol 3.0, 6 cyl. Currently seeing 32mpg but only runs right on shell v power. Employer pays 28p/mile fuel only.

At £1.40 per litre your fuel cost is just under 20p per mile, so you are making 8p per mile driven.

 

[flango]

At £1.40 per litre your fuel cost is just under 20p per mile, so you are making 8p per mile driven.

removed due to incorrect information and did not want to mislead others

 

[Dieselman]

there are also a couple of additional benefits with LPG.


Apart from a higher octane, it is also a gas as it enters the cylinders and not a liquid like petrol, so the oil is not affected by bore wash, which means less engine wear.

As always there are downsides too.
Due to lack of the liquid fuel cooling the valves, they have a tendency to burn the valve seats.

 

[Dieselman]

No he's making 25p per mile , because although his employer pays 28p per mile HMRC rates are 45p per mile so you can claim the other 17p per mile back from them for the first 10,000 miles although it's 25p per mile after the first 10K so he would be profiting which also has to be declared to them.

Switch to LPG and the his costs are around 10p per mile driven so now making 18p per mile or 35p per mile taking into account the first 10k including HMRC payback

You can't claim 45p per mile from HMRC, you can be paid a maximum tax free payment of 45p per mile.
If the rate paid for the total reimbursement of the car is less than 45p per mile you can only recover the tax difference between the two values.

 

[flango]

As always there are downsides too.
Due to lack of the liquid fuel cooling the valves, they have a tendency to burn the valve seats.

Gen4 systems use flash lube which prevents valve seat recession, cleans valve seat deposits and gives better valve cooling through the valve seats so this is no longer a problem like it used to be.