Shocked by difference in fuel consumption (1 Viewer)

[Badknee]

A motorhome is about as aerodynamic as a brick ..
So it makes sense.
Mitch.

Very true, A class and bed over cabs take some pushing along.

 

[WillH]

When I was a Marine engineer most of the time we sailed at 16 knots for economy. On the odd occasion we would get a 'hurry up' and push the engine to 26 knots, fuel consumption more than doubled. This was logged using calibrated equipment. I suggest that for wind resistance on a motorhome 56 mph or thereabouts is the land-based equivalent of 16 knots. Its also my cruising speed on motorways. We average around 30 mpg on a tankful including the slow bits. On a windy day this easily drops to 25/26 mpg.

 

[Scattycat]

Just did an extended fuel consumption test.

2015 Fiat 2.3 150bhp
6 speed manual - cruise control
Weight 4 tons
Full day driving on the same road

70 mph (2500 revs) - 23mpg
57mph (2000 revs) - 30mpg

A little less speed, saves a lot of fuel

Just a word of caution,as has been mentioned in previous threads. When the engine is pottering along at around 2000 revs you stand a good chance of it sooting up. I have been advised by folks much more learned than me that this can be one of the causes of the dreaded "engine management light" coming on and dropping the engine into limp mode.
The erg valve soots up and garages love to charge you mega bucks for a replacement when often they just strip down the old one and clean it.
Diesel engines need to work to be efficient. Under advice from those in the know we now when on the run we try and keep the revs just under 2500/2750 and fuel consumption taken from tank full to tank full on our 2.2 citroen is between 25mpg and 30mpg depending on the terrain.
Anyway, it works for us

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[Badknee]

Just a word of caution,as has been mentioned in previous threads. When the engine is pottering along at around 2000 revs you stand a good chance of it sooting up. I have been advised by folks much more learned than me that this can be one of the causes of the dreaded "engine management light" coming on and dropping the engine into limp mode.
The erg valve soots up and garages love to charge you mega bucks for a replacement when often they just strip down the old one and clean it.
Diesel engines need to work to be efficient. Under advice from those in the know we now when on the run we try and keep the revs just under 2500/2750 and fuel consumption taken from tank full to tank full on our 2.2 citroen is between 25mpg and 30mpg depending on the terrain.
Anyway, it works for us

While I understand the thinking I don't do that. I will regularly run it up to 3000rpm through the gears but no higher and 2000/2200 cruising. As an ex HGV driver day in day out @56mph the revs are about 1500/1800 rpm.

 

[WillH]

To limit soot build up, change down a couple of gears when you hit a real hill and get the exhaust temperature up to burn out the soot. A long hill is best.

 

[Steve devon]

While I understand the thinking I don't do that. I will regularly run it up to 3000rpm through the gears but no higher and 2000/2200 cruising. As an ex HGV driver day in day out @56mph the revs are about 1500/1800 rpm.

I'm hgv as well, just let them slog a bit on hills , that will keep em clean .just come back from Spain 2500 mile trip on crappy French super market deisel, no probs . I can't get my head around how clean the inside of the exhaust pipe is , 7500 miles and it still looks like new, 5 years ago it would be black with soot

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[Badknee]

I'm hgv as well, just let them slog a bit on hills , that will keep em clean .just come back from Spain 2500 mile trip on crappy French super market deisel, no probs . I can't get my head around how clean the inside of the exhaust pipe is , 7500 miles and it still looks like new, 5 years ago it would be black with soot

Does it run with Adblu? That's the zorst cleaner.

 

[maison]

With a low profile Fiat 2.3 we can achieve up to 33 mpg on Motorways at 60 to 65 mph, but more usual average is 26 to 28 mpg.

No need to go tearing about on normal roads so enjoy the journey. Many of the best villages we have found in France have been by accident. Although we do use Satnav Mrs Maison likes a map and tends to say " Take the next left. It looks like an interesting road." Sometimes her "interesting" turns out to be my "terrifying", but we have seen some very interesting places over the years.

 

[Steve devon]

Does it run with Adblu? That's the zorst cleaner.

I don't think so, it's euro 5 , so not sure

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[Badknee]

No need to go tearing about on normal roads so enjoy the journey. Many of the best villages we have found in France have been by accident. Although we do use Satnav Mrs Maison likes a map and tends to say " Take the next left. It looks like an interesting road." Sometimes her "interesting" turns out to be my "terrifying", but we have seen some very interesting places over the years.

Angela is the same as my grey hairs can testify

 

[Badknee]

I don't think so, it's euro 5 , so not sure

No sorry I thought we were talking HGV.

 

[ianandkath]

i just stick on the cruise control, 60 mph,1500 rpm, and the good news is,,,,,,,,,, watching the fuel meter go down bloody quickly.
dash reads 9 mpg all the time, think its stuck

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[Badknee]

i just stick on the cruise control, 60 mph,1500 rpm, and the good news is,,,,,,,,,, watching the fuel meter go down bloody quickly.
dash reads 9 mpg all the time, think its stuck

I once worked for a haulage company who bought a fleet of Scania's because they did eleven to the gallon instead of the nine mpg our Mercs were doing.

 

[ianandkath]

my old leyland marothon 2 did 6 mpg empty, 4 mpg loaded.
it was a breakdown truck with a 500hp cat, but pulled like a train with 48 tons on suspended tow

 

[gus-lopez]

My old Hymer 2.5td has averaged 26 mpg over the last 4,500 miles. Similarly, I rarely exceed 60mph and mainly drive at HGV speeds on dual carriageways/motorways.

Good idea here as 100kph is the m/way limit. for Mhomes.
See 2,A, 4.
Broken Link Removed

Just a word of caution,as has been mentioned in previous threads. When the engine is pottering along at around 2000 revs you stand a good chance of it sooting up. I have been advised by folks much more learned than me that this can be one of the causes of the dreaded "engine management light" coming on and dropping the engine into limp mode.
The erg valve soots up and garages love to charge you mega bucks for a replacement when often they just strip down the old one and clean it.
Diesel engines need to work to be efficient. Under advice from those in the know we now when on the run we try and keep the revs just under 2500/2750 and fuel consumption taken from tank full to tank full on our 2.2 citroen is between 25mpg and 30mpg depending on the terrain.
Anyway, it works for us

At 2000rpm my car is doing 75mph. At 2750 rpm we are up over 90mph.

To limit soot build up, change down a couple of gears when you hit a real hill and get the exhaust temperature up to burn out the soot. A long hill is best.

Doesn't matter what speed you do in my car when you go to open the boot the exhaust will take the skin off your foot. Ask me how I know.

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[Steve devon]

My boss has just bought a new euro 6 Scania, and was told that what comes out of the exhaust pipe is cleaner than what goes in through the intake ,, crazy!!

 

[Scattycat]

Good idea here as 100kph is the m/way limit. for Mhomes.
See 2,A, 4.
Broken Link Removed


At 2000rpm my car is doing 75mph. At 2750 rpm we are up over 90mph.


Doesn't matter what speed you do in my car when you go to open the boot the exhaust will take the skin off your foot. Ask me how I know.

Then may be you should be in a lower gear. Who knows I'm no expert(?)

 

[Allanm]

I'm hgv as well, just let them slog a bit on hills , that will keep em clean .just come back from Spain 2500 mile trip on crappy French super market deisel, no probs . I can't get my head around how clean the inside of the exhaust pipe is , 7500 miles and it still looks like new, 5 years ago it would be black with soot

Our exhaust pipe, at 18000 miles, is sparkly clean inside too. Haven't seen a drop of soot, dust or anything inside it, and that's almost 100% on cheap French supermarket fuel, and averaged around 27 mpg from new.
We mainly keep to around 60 mph.

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[WillH]

Not the exhaust temperature, I should have been more specific, the exhaust gas temperature. This needs to be high to burn off the soot and other non-combustibles. We are talking 550C plus.

 

[Charlie]

My boss has just bought a new euro 6 Scania, and was told that what comes out of the exhaust pipe is cleaner than what goes in through the intake ,, crazy!!

Our Toyota Rav4 (new shape) puts out cleaner air than goes in... Still expensive VED though as the greedy sods rob us blind !

 

[Frentchy]

Proctology...had to look it up, thanks to google

Here's a bit more........drag force is proportional to velocity squared

57 mph.....drag 3250

70mph....drag 4900

in other words 50 % increase in drag, other factors will affect fuel consumption so a 30% decrease in fuel consumption seems OK.

With all these calculations of permutations and coefficients of air drag and bow waves diminishing the vehicles forward speed by a % governed by the % of added acceleration. Can anyone calculate how fast you would have to go to enable you to meet yourself coming back.

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[Jimbohorlicks]

This forum is fantastic-learn something new every day -go faster use more fuel-wow

 

[gus-lopez]

My boss has just bought a new euro 6 Scania, and was told that what comes out of the exhaust pipe is cleaner than what goes in through the intake ,, crazy!!

Yes & it has been like that for years & yet they still want to impose further 'improvements' ?

Then may be you should be in a lower gear. Who knows I'm no expert(?)

Unfortunately it is an auto.

 

[ianandkath]

With all these calculations of permutations and coefficients of air drag and bow waves diminishing the vehicles forward speed by a % governed by the % of added acceleration. Can anyone calculate how fast you would have to go to enable you to meet yourself coming back.

warp speed,,, ask mr scotty

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[laurieash]

I try to avoid soot up by on large hill hold in a lower gear that I can negotiate the hill without having to change down or up on the hill.
saves on half shafts/clutches.
For them that still have halfshafts.

 

[bertiebasset]

Not sure what mileage we used to get on HMS Resolution but we only refuelled every 5 years or so.
In the motorhome now I manage almost 30mpg travelling at a high speed around 2000 revs/ 58mph on the dash (55mph on the satnav). Works for me as I am now retired and will spend another 8 weeks meandering around Europe this Spring/Summer.

 

[Badknee]

Not sure what mileage we used to get on HMS Resolution but we only refuelled every 5 years or so.
In the motorhome now I manage almost 30mpg travelling at a high speed around 2000 revs/ 58mph on the dash (55mph on the satnav). Works for me as I am now retired and will spend another 8 weeks meandering around Europe this Spring/Summer.

Sounds like a plan.

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[Lenny HB]

We run with the sat nav and dash cam showing the speed. In truth they both show the true speed is four mph lower than what the van speedo says, so your 70 mph is 66, and 57 is 53. We travel at a true 62 mph in a 4.3 ton scout, and getting 25.5 mpg

I don't believe you, I've never seen a Fiat speedo that accurate, they are normally +10-12%.

 

[Dorwyn]

As I'm contemplating a new x290 I'm rather concerned about the low figures quoted here. My present high top camper van seems to do about 34 mpg over long trips, often with quite high touring speeds. I don't quite know how the ships and RVs (about the same consumption?) got in there but it's good fun.

 

[Lenny HB]

As I'm contemplating a new x290 I'm rather concerned about the low figures quoted here. My present high top camper van seems to do about 34 mpg over long trips, often with quite high touring speeds. I don't quite know how the ships and RVs (about the same consumption?) got in there but it's good fun.

When spending £50k-£100k on a new van and with the mileage Motorhomes do, in most cases less than 8000 a year the fuel cost is fairly insignificant in the overall running costs.

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