M5 (E39) + LPG = Sacrilege?

M5 (E39) + LPG = Sacrilege?

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Discussion

Zwolf

Original Poster:

25,867 posts

206 months

Monday 25th August 2014
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I seem to recall a few of the owners of these on here have converted their M5 to run LPG for higher mileage use.

I'm considering the same, albeit on an as yet unbought example, or simply converting the E38 750i I currently use, as a result of moving and having a 100 mile/day commute of mostly A-road and motorways and pathologically opposed to going diesel. As good as a 530d is, it just isn't remotely special in the way a V12 or M V8 is during driving time away from the commute.

Some may consider it a "waste of an ///M car" and the Seven better suited to the role, however I only have one space so a choice must be made and stuck to at least for as long as it takes to justify the cost of conversion, but ideally a situation I'd be keeping for at least a year or two and 30-60k miles from present mileages (currently 120k on the Seven, looking at M5s in the £7-8.5k range, mostly 120-150k mile examples, provided current mechanical condition is sound).




toasty

7,466 posts

220 months

Monday 25th August 2014
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Seems perfectly good to me. Palmersport run their M3s on LPG and they seem to go alright.

DennisCooper

1,340 posts

171 months

Monday 25th August 2014
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Hi,

It is possible and if you feel it's worth it, then go for it and don't worry a bean about what anyone else thinks!

However think of the bigger picture, you'll be using is as a daily 'beater' car, racking up miles, most likely often just 'sitting' in traffic, and on a AM and PM rush hour use time, not really much chance of 'stretching' the car to what it's capable of. In this regard, it is bit of a mismatch to what the car is and capable of and what it'll spend 98% of the time doing. On top of that, you'll have the cost of the conversion and it's maintenence costs on top of the 'relatively' expensive M car maintainence costs as well. Given all that, you can see why perhaps less than a handful of E39 M5's have an LPG system.

A 750i is perhaps the better candidate what with it's superior levels of comfort for commuting work/use, so out of the two, I'd say that's the one to consider putting to LPG. When it comes time to sell, with the potentially starship mileage the 750i will have, it'll stand a better chance of selling than a starship miled, LPG example of an E39 M5.

The choice, it up to you!

Cheers, Dennis!

RichardM5

1,736 posts

136 months

Monday 25th August 2014
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I'd have thought a manual 540i would be a better choice than an M5.

Cemesis

771 posts

162 months

Monday 25th August 2014
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Or an Auto 540i.

http://www.autotrader.co.uk/classified/advert/2014...

Change the trim, put a MK4 Nav and the widescreen and you'll be set. You can even fit the bluetooth ULF.

Crap, sorry, just realised who you are so you probably know all that anyway.

The M5 is great (I should know) but is it 4 times better than the car I've linked here? No.

Lowtimer

4,286 posts

168 months

Tuesday 26th August 2014
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I think doing the 750i instead would be smarter. It will pay back quicker, and will help to shift that when the time comes - whereas I think more people would be put off (probably unnecessarily) by an LPG conversion on an M5

sydown

63 posts

209 months

Friday 29th August 2014
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I have run a e39 540 m sport on LPG for about 5 years now and will only get rid when it really fails 190K miles so far! The two cars you suggest are problematic as only prins or brc injectors will cope with the 50bhp per cylinder of an E39 m5 without running lean at top end and the 750 will be expensive to convert as you will probably need 2 V6 kits to convert!! My mate runs a E60 550 on brc and at 367 bhp the car does get a tiny bit lean at full throtle on full load! However when you need to you can always switch back to petrol in less than a second!! I used Solihull autogas for my conversion and the chap was happy to give as much advice as possible before i commited to anything!

Zwolf

Original Poster:

25,867 posts

206 months

Friday 29th August 2014
quotequote all
sydown said:
I have run a e39 540 m sport on LPG for about 5 years now and will only get rid when it really fails 190K miles so far! The two cars you suggest are problematic as only prins or brc injectors will cope with the 50bhp per cylinder of an E39 m5 without running lean at top end and the 750 will be expensive to convert as you will probably need 2 V6 kits to convert!! My mate runs a E60 550 on brc and at 367 bhp the car does get a tiny bit lean at full throtle on full load! However when you need to you can always switch back to petrol in less than a second!! I used Solihull autogas for my conversion and the chap was happy to give as much advice as possible before i commited to anything!
Interesting stuff, thanks. Having spent most of today smoking around in the E38, I'm in agreement with most here that it's the more suited and sensible one to convert and I should wait until home and work are closer together and just enjoy an ///M as it should be.

The running lean at top end I'm not too concerned about in either case as when it's running on LPG it'll just be cruising along ad normal motorway speeds, below 3k most of the time and the V12 isn't about it's top end really. It'll be run on unleaded sometimes too, to keep that part of the car's mechanicals running as they should and hopefully preclude the tank turning to Swiss cheese, a particular E38 problem.

Cheers chaps, sensible decision reached. The most local company I've found - as recommended by a neighbour - is Capital Auto Gas in New Malden and they seem to use BRC kit. I requested a quote for a 12 cylinder installation as they only list 4,5,6 and 8 on their website. Three days later I'm still waiting for contact. Not too impressed at that.