# Various Engines and Their Economy



## 116388 (Sep 6, 2008)

Hello again,

I've been looking on Ebay a lot lately in search of my first MH and am astounded at some of the sellers claims of the MPG they achieve! It seems nearly every large diesel and petrol MH gives 'an incredible' 35-40mpg!

Can a 20 year old Mercedes 4ltr turbo diesel realistically give 28+mph?

.... and can a 1.8 turbo diesel Citroen Romahome with 95K miles really give me 50mpg on a steady run? I've also seen 45mpg claims of the 970cc Bedford Bambi.... is that likely for a little 1.5ton MH?

..... and what about the 1.7 petrol Renault high top, is 35-40mpg an honest quote do you think?

..... I'm definately dubious of 6.0 and 7.4ltr V8 American RVs that are well over 30ft and achieving 16mpg if driven sensibly, at least double that with LPG.... surely not?

So, can someone please dispell the myths and highlight the truths for me because I'm quite certain that several Ebayers are picking figures out of the air when advertising!

Lastly, what is deemed the most economical MH/camper on average for it's size, weight and luxury?

Many thanks,

Shane.....


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## Vennwood (Feb 4, 2007)

If you want to get some idea of MPG then look on here at the logbook feature - you will get a more honest view than the wild claims on Ebay

Pete


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## raynipper (Aug 4, 2008)

Hi Pete,
I have often looked at your 22.43 mpg and wondered how you get that?

Ray.


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## trevorf (May 16, 2005)

I think you are approaching your buying decision from the wrong angle. There are more important factors to consider than a couple of MPG here or there. You need to set yourself a buying budget and then decide what size and layout you really want. 

Trevor


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## b16duv (Feb 14, 2006)

What Pete said!

As a very rough guide: -

2.0 - 2.3litre engines 25 - 30mpg

2.8 - 3.0 litre engines 20 - 25mpg

Over 3 litre mid teens mpg

6 litre around 10 - 12mpg if manual, less if torque converter auto.

The higher the van, the worse the mpg

Bigger engine = bigger van both weight and length.

Petrol engined RV's 6 -10mpg

Diesel Pushers eg cummins 6 Litre with allison auto maybe 8 mpg.

The slower you drive, the better the mpg

David


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## 116388 (Sep 6, 2008)

Thanks Pete, Ray, Trevor and David.

I totally agree that there are more important factors than mpg to consider. It's just frustrating that some sellers, no doubt sincere, are naive in their assumptions.

Anyway, David, you say the taller the vehicle the less mpg it will achieve, that makes sense. However, I have thought about converting a LDV high sided Luton van with above cab wind deflector into a jolly camper, how much difference would you expect between a high top LDV (about 12" higher than the normal LDV) and a Luton boddied LDV, both with the Transit 2.5ltr diesel? BTW, do the LDVs have a decent enough reputation? I think they look nice.

Thanks,

Shane.....


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## b16duv (Feb 14, 2006)

Shane,

I would think there could be between 15 and 20% difference in fuel consumption between the high top and a luton. The wind deflector can make a difference of course, but it depends on the wind deflector.....

Personally, I'd look for a more modern van than the LDV for a conversion. I think there is a forum section on self-builds and there is also a club for them too.

David


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## GerryD (Sep 20, 2007)

I know that motorhome manufacturers never publish mpg figures but be very wary of anyone who does.
In fact the Advertising Standards Agency is currently investigating mpg claims by car manufacturers following complaints raised by myself and others about the alleged mpg on the current Smart. Smart claim fuel consumption of 60.1 as typical, whereas you will often have to make do with 38-45mpg average.


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## paulkenny9 (Jun 25, 2008)

hi

we run a soon to be 24 year old mercedes 207 coachbuilt with the 2404cc engine, 
if we sit at fifty (not very often) i reckon it hits about 25mpg, most of the time we sit between 60 an 65 and it returns about 22.

i have seen the similar vans on ebay with reports of 30 to 35 which i doubt very much.

i agree that the mpg isnt/shouldnt be much of a factor (unless its something silly like 10) when buying a van, it costs what it costs.

we did a 3300 mile trip in the summer an it coost us aroud 900, that was when diesel was 1.20 here, were haedin down to spain next week so we should nitice the difference in the fuel prices.

about the ldv, i know it has a relible transit engine but i wouldnt, my good lady has had 2 hightop ldv minibuses an they always seemed to be in the garage with non engine related problems, suspension an steering also gearbox, why not go the hole hog and have a transit?

Paul


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## 116388 (Sep 6, 2008)

Thank you all again for these replies. David, 15-20% is more than I expected. I will visit the self build forum tomorrow.

Paul, I know the Transit is a very good vehicle but the LWB Jumbo is still very expensive second hand and that's the one I like. Points taken regarding the LDV though, thanks.

You mention your 2.4 diesel Merc, my parents had a panel van conversion Merc with the 2.4 way back in '91 and they loved it. Wished for a bit more umpf but otherwise swore by it for reliability and decent fuel return, about the same figures as yours BTW. What do you reckon to the 4ltr diesel Merc for mpg and reputation? Will there be much difference between the 2.4 and 4ltr engines?

Shane.....


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## paulkenny9 (Jun 25, 2008)

yeah, our van slows right down on up hills, but other than that its what i would expect, its only 2800kg so fairly light compared to others, even with our gear in i weighed it and we were just under.

its got strong lower gears, an a first which is only used when pullin of hills, so i am sure it would get up any hill,

once we tried to to pull a pack of breeze block up a not very steep hill in a 95 2.4 transit and it faled, i don think the 207 would have that problem, an it was desighned in the mid 70s.

dont know about the 4 litre, i dont really see a need for a enigine that size when its only gonna hit similar speeds, i imagine the mpg cant be that much lower than what i get cos the engine aint workin as hard.

i would recommend the engine in my old van


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## Vennwood (Feb 4, 2007)

raynipper said:


> Hi Pete,
> I have often looked at your 22.43 mpg and wondered how you get that?
> 
> Ray.


Well Ray,

I drive very light footed, keep off minor roads and cruise around 55mph. As I have said in many posts on this site. If I go above 60mph it drops to around 18mpg. If I go slower than 55 it makes no difference. Also I try to keep on dual carriageways. The worst type of roads are ones with lots of roundabouts or crossroads where you have to slow right down or stop and start. Then we drop down to mid teens. Most of my fill ups so far have been on long European trips which may be giving a better figure than say if my trips had been in UK travelling down to somewhere like Cornwall

I have thought about going for a remap but can't justify the cost verses return. I'm quite happy with my 22mpg. Over time I expect it to drop slightly to around 21. Even that isn't bad for a 3 ltr motor.


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## mikeyv (May 23, 2007)

Another vote against the LDV here - we had Transit and LDV minibuses to get to jobs - I occasionally drove, and have to say the LDV was a most unpleasant thing to drive, or be driven in, and as said previously, very unreliable compared to the Transits.


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## dees46ex (Jul 31, 2008)

*economy*

Hello Shane
If i was converting i would be looking for a petrol vehicle,convert to gas and fit a big tank or tanks.It amazes me that no manufacturer has as yet provided a petrol based chassis for mh build.
The americans do,but 5,6 7 or 8 litre engines are just stupid.Our local council uses gas fuelled bin lorries and they are so much quieter than derv.
It must be possible to get a large petrol van somewhere.If fuel economy is a prime concern then gas is the way to go
kind regards
damien purcell


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## androidGB (May 26, 2005)

Vennwood said:


> I drive very light footed, keep off minor roads and cruise around 55mph. As I have said in many posts on this site. If I go above 60mph it drops to around 18mpg. If I go slower than 55 it makes no difference. Also I try to keep on dual carriageways. The worst type of roads are ones with lots of roundabouts or crossroads where you have to slow right down or stop and start. Then we drop down to mid teens. Most of my fill ups so far have been on long European trips which may be giving a better figure than say if my trips had been in UK travelling down to somewhere like Cornwall
> 
> I have thought about going for a remap but can't justify the cost verses return. I'm quite happy with my 22mpg. Over time I expect it to drop slightly to around 21. Even that isn't bad for a 3 ltr motor.


I'm glad I've found someone else whose vehicle, like mine obeys the laws of physics

Andrew


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## Bagshanty (Jul 24, 2005)

GerryD said:


> I know that motorhome manufacturers never publish mpg figures but be very wary of anyone who does.
> In fact the Advertising Standards Agency is currently investigating mpg claims by car manufacturers following complaints raised by myself and others about the alleged mpg on the current Smart. Smart claim fuel consumption of 60.1 as typical, whereas you will often have to make do with 38-45mpg average.


38-45!!!! On a Smart car? We consistently get 50.6 on our 5 year old Toyota Yaris 1.5 litre!

... and 28-30 mpg on a 2006 Fiat 2.3 JTD


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## 116388 (Sep 6, 2008)

*Re: economy*



dees46ex said:


> Hello Shane
> If i was converting i would be looking for a petrol vehicle,convert to gas and fit a big tank or tanks.It amazes me that no manufacturer has as yet provided a petrol based chassis for mh build.
> The americans do,but 5,6 7 or 8 litre engines are just stupid.Our local council uses gas fuelled bin lorries and they are so much quieter than derv.
> It must be possible to get a large petrol van somewhere.If fuel economy is a prime concern then gas is the way to go
> ...


Thanks Damien, do you mean LPG gas and running the engine and appliances all from the same LPG tank?

Shane.....


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## dees46ex (Jul 31, 2008)

*economy*

Yes Shane
People seem to have concerns about changing to this way in case the gov just ups the tax on gas as well.
I doubt very much if this will happen,if only because of the environmental reason.
It just seems to me to be a really economic option,most of europe has easily available pump gas,and of course you would retain a small petrol tank.
kind regards
damien purcell


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## ingram (May 12, 2005)

Simplelife said:


> Hello again,
> 
> .... and can a 1.8 turbo diesel Citroen Romahome with 95K miles really give me 50mpg on a steady run? I've also seen 45mpg claims of the 970cc Bedford Bambi.... is that likely for a little 1.5ton MH?
> 
> Shane.....


I think some of these figures are 'optimistic' :^o but my 1985 Citroen BX 1.9 diesel * did* always do 50mpg however I drove it so I believe that Romahome figure may be the most accurate there. It's probably the similar to BX 1.7 turbodiesel.

My 1992 Renault Master 2.5 non turbo diesel averages 25 to 26mpg and my 2006 2.8 Autocruise does about the same: I don't do rushing: in the Renault because I can't and in the 'cruise because I don't want to.

Harvey


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## SpeedyDux (Jul 13, 2007)

I'm not an engineer, but it seems to me that you can achieve a certain improvement in fuel economy by efficient engine design and reducing power losses where possible. Manufacturers have probably taken that as far as it will go, so we are probably expecting only small incremental improvements in engine efficiency from now on. 

The biggest factor in fuel economy is just simple physics. It doesn't take a lot of fuel to keep an efficient vehicle at a constant speed, on a level road. Getting up to that speed is what matters, and even more importantly, the loss of energy involved in braking the MH to a halt again.

Kinetic energy = 1/2 M V squared. So the energy you use (fuel) to get the MH to a certain speed is proportional to the Mass of the vehicle, but more importantly proportional to the square of the velocity. 

The more payload you carry the more fuel is required to provide the necessary kinetic energy to get up to your cruising speed. The proportional square law means you need vastly more fuel to propel that mass to 80 mph than 60 mph if your motorway cruising speed is 80mph. 

Apart from better aerodynamic designs and use of lighter materials to obtain significant weight reduction in MHs, the most promising area it seems to me for significant economy gains in future should be regenerative energy systems to recover kinetic energy that would otherwise be turned into heat by brakes. Car manufacturers have been researching this and we may see some cars soon that feature this. Hopefully that technology should find its way into a new generation of base vehicles.  


SD


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## raynipper (Aug 4, 2008)

Hi Pete,
Now I realise I was wrong in assuming your rig was an American Flair with a 7.4 or 5 litre V10.
I must get stronger glasses.

All my American RVs be they petrol or diesel managed 9 to 10 mpg. normal use. But oh boy did the numbers change when empty.

Ray.


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## 116388 (Sep 6, 2008)

b16duv said:


> What Pete said!
> 
> As a very rough guide: -
> 
> ...


David,

A chap on Ebay has a nice 1984 22ft GMC 6.2 V8 diesel and claims 16 in town, 25 mpg on the open road. What do you think?

Thanks,

Shane.....


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## raynipper (Aug 4, 2008)

Hello Shane,
The original GMC RV was great and had a 7.2 Litre V8 gas engine. It could achieve 14/16 mpg (imperial) driven carefully.
If this one has the 6.2 Chevy diesel engine installed it's a replacement for the petrol one and never was successful. I can't vouch for the mileage claims but it will a problem.
The GMC is regarded as a 'Classic' and has a large following. There are various forums devoted just to this RV stateside. 
Although a brilliant concept in it's day and construction of aluminium and fibreglass there is a lot of wood used in the body frame. Beware this can deteriorate over 20 years.
Apart from this it had very little storage space. the suspension air bags are incredibly expensive to replace. Brakes were always a problem also.

But a great looker.

Ray.


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## b16duv (Feb 14, 2006)

Simplelife said:


> b16duv said:
> 
> 
> > What Pete said!
> ...


Shane,

Happy New Year!

I would have thought 25mpg from a 6.2 diesel very unlikely. My mate put one of these in his landrover some years ago and it was a disaster! I'd steer clear of a vehicle with an engine conversion unless it's been done by a reputable firm and comes with a warranty.

David


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## johnc (May 1, 2005)

Simplelife said:


> Hello again,
> 
> I've been looking on Ebay a lot lately in search of my first MH and am astounded at some of the sellers claims of the MPG they achieve! It seems nearly every large diesel and petrol MH gives 'an incredible' 35-40mpg!
> 
> ...


My old 1991 Renault Trafic petrol 2 litre coachbuilt gave 16 to 18 MPG regardless of how I drove it.

My new Peugeot 2.2 litre gives the following

35 MPG on normal roads where there is no great hill climbing involved.
32 MPG up Northon on hills etc
30 MPG @ 65 to 70 MPH on motorway
26 MPG @ +80 MPH (where allowed)

John C


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## Jean-Luc (Jul 21, 2005)

Just back from 6K+Km trip to Spain/Portugal. No tolls, hence many towns, roundabouts etc. Weight just under GVW (3850Kg), engine 2.8 JTD Power (147bhp), 45k Km on the clock. Average MPG for the trip was 25.5


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## 116388 (Sep 6, 2008)

First time on MHF for ages, about time I said a few thankyous! Thank you everyone fore your help.

Shane.....


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## 38Rover (Nov 9, 2006)

2.3 FIAT Multijet on Burstner Solano t700 low profile 3,5000kg

On motorways or similar 70/80 23mpg
On motorways 60/65 28mpg


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