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Discussion Starter #1
Folks

I am weighing up the above dilemma for my first 300C and would be interested to hear your views. I spend a fair bit of money on fuel and so economy is important (although clearly not that important otherwise I would not want a 300C!).

Specifically I am comparing the running costs of a 3.0 diesel compared to a 3.5 V6 on LPG / petrol. The former's official figures are 34 / 35mpg whereas I know from another forum member that the latter will achieve 20mpg on average (=40mpg because LPG is 62p a litre locally). Road tax is likely to be higher on the LPG if post-2006.

Another feature is that the petrol / LPG versions seem to be lower mileage for the same money as the diesels. The diesel is quite a bit quicker on the 0-60mph and will have a bigger tank hence better range.

I am not sure from other posts here whether a diesel remap makes any difference to economy - there seems to be a view from some that they are ineffective but I would be interested to hear thoughts.
 

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If i had the choice of the slow 3.5 or diesel, id go the diesel way,if you do all motorways then 37mpg is easy as thats what i get on a run, remap maybe but all depends how you drive.

So the pro's i can see for the 3.5 is it doesnt sound like a bag of spanners....lol, maybe a little better on the wallet as petrol is cheaper than diesel.
cons slow, and like you say could be £450 road tax, and a small dounut tank

Also if you are paying full price for the conversion, its going to take 200000 miles to break even.
 

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No i mean 200,000 if you have to pay £1500 ish to convert so then once converted you would be 3-5mpg better off the a than a diesel, so say 5mpg better it going to take a many thousands of miles to get the £1500 back

So it more like 80,000 to be fair....
 

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I won't go into the ball point figures but as a guide I run a 5.7 V8 with the mds switched off. I now pay around £30-£34 gas when it used to cost me about £60 unleaded per week. My running costs are slashed by around half and in my case I reckon the parts will pay itself off within the next 2 months.
 

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Agree with your observations although take it you mean 20,000 not 200,000 miles for payback.
You need the 5.7 or 6.1 to benefit from LPG otherwise like Paul said - get a diesel. I have the Diesel with a remap and I average 38-40mpg - I cover about 25k a year and always with a big smile on my face
 

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I am with badgx on this . Had my London Taxi with LPG & my last 2 Range Rover's . SO so cheap to run and if you run on gas most of the time the oil is so clean even after 10 0r 20,000 miles !!! You will run a 6.1 on Ford Escort money ! PAT
 

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Just to throw a spanner in the works. I've had 2 lpg powered cars, one with a Prins system but I don't recall the make of the other. I had issues with both, and the biggest problem was deciding whether it was an engine or lpg issue. In my experience lpg is a specialist job so the mechanics blame the lpg, and the lpg guys say its fine its an engine issue. To be honest, I would go for the CRD, no complications.

Sent from AutoGuide.com Free App
 

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Today lpg kits are all sequential, direct port injection to cylinder system for faster switching and very reliable. Not everyone use the old single port injection systems, although they may be found in some 3rd world countries which run LPG/CNG systems.

If there is a fault with the lpg kit, you simply run diagnostic program to determine trouble code, i.e. like the photo below. If it were a fault with the car, you run diagnostic via obd2 port, i.e. predator to determine code.

 

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Discussion Starter #10 (Edited)
No i mean 200,000 if you have to pay £1500 ish to convert so then once converted you would be 3-5mpg better off the a than a diesel, so say 5mpg better it going to take a many thousands of miles to get the £1500 back

So it more like 80,000 to be fair....
I think what this calculation ignores is that, like for like, diesels seem to be about £1,500 more expensive than V6 petrols.
 

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Just get a Hemi, and if you have space, get a cheap-tax, cheap banger or fun car to sit alongside. My SLK does 40mpg and costs £450/year to tax AND insure. It cost as much as a good LPG conversion, but is also a convertible; you can get an MX5 on classic insurance and slash those figures. On a run the Hemi should hit 30mpg easily with MDS behaving. Otherwise get a CRD. Unless the power delivery of the V6 petrol has changed drastically from the 300M (I believe it's the same engine) then it's totally unsuited to the style and weight of the car, needs to be revved hard and is thirsty, worse than a 5.7.

FWIW, I get 23mpg AVERAGE on my 5.7, including the inevitable short runs. I don't hoof it away from the lights, but it does get driven quite fast on A-roads, and motorways I've found 28mpg if you want to push the buggers out of the outside lane, 31mpg+ if you're happy to dawdle and leave a gap for people. It's dropped recently because a caliper or e-brake shoe is dragging slightly.
 
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