fuel consumption

[bopeep]

Is it better to have the load in your car or in your caravan for better consumption. I have just been on a trip, I loaded the car, with the majority of equipment made sure the nose weight was correct on the caravan and set off. A 200 mile journey I got 23, as we had unloaded most of the gear into the caravan our moving on three days later to another campsite and the car was much lighter I got 26 and the weight was in the caravan.
Nothing was overloaded all well within our guidelines, on our return home we again stuffed everything in the car and our consumption dropped. I know it could be a lot to do with roads and wind and traffic, but we are talking about no wind, no traffic and no mountains. We are abroad of course.
I was wondering what other peoples thoughts were on this subject It was no means a proper survey just the way it happened as it was a new outfit and I am a novice at caravanning, perhaps there is a set formula that the more experienced work to.
My caravan was in storage so I did not bother to unpack from the car until our first campsite. We decided as I was unwell to leave suddenly one morning from the last campsite and chucked all the things in the back of the car.
Is there a standard procedure?
Thanks

 

[prjohns]

There are so many variables to take anything meaningful from your mileage difference. A few examples are- how tired you are, distance travelled, different petrol and air temperature are just some factors that affect MPG. Ther are many others.

But I do agree with your request is there any info that gives advice on increasing MPG and where the weight should be for best performance.
and
What affect does 1kg increase in weight have on MPG.

 

[bopeep]

When we picked up the caravan from the dealer in london we drove to the midlands and both the car and the caravan was empty, there was a bit of traffic about on the M1 and I got 30 to the gallon, all this is according to the consumption gauge on the speedo.
Travelling down to Spain there was of course the shopping and all the tin food, all the goodies from English shops and gallons of water, why I have no idea, plus all the things we bought from the caravan show at the NEC, we were pretty loaded as we were going home. but we still got about 24.
The last day I kept going and did 14 hours non stop to get home so I was pushing it.
I would be interested what 1 kilo difference would make.

 

[JohnGriffiths]

One thing that might make a difference are tyre pressures. Most cars have an upper and lower pressure limits depending on whether the car is lightly loaded or heavily loaded. If you run the car heavily loaded with the the lower pressure the rolling resistance of the tyres will be higher and give poorer consumption. Caravan tyres are usually just left at the pressure suited to when it is fully laden so adding weight there would make less difference.

 

[Surfer]

When we picked up the caravan from the dealer in london we drove to the midlands and both the car and the caravan was empty, there was a bit of traffic about on the M1 and I got 30 to the gallon, all this is according to the consumption gauge on the speedo.
Travelling down to Spain there was of course the shopping and all the tin food, all the goodies from English shops and gallons of water, why I have no idea, plus all the things we bought from the caravan show at the NEC, we were pretty loaded as we were going home. but we still got about 24.
The last day I kept going and did 14 hours non stop to get home so I was pushing it.
I would be interested what 1 kilo difference would make.

What sort of mileage do you get when you are not towing? Do you know the MTPLM of the caravan?

 

[ProfJohnL]

Hello Bopeep

How are your sheep

?

Car manufacturers have standard tests for the assessment of fuel consumption, but these are carried out under very controlled laboratory conditions, and so it is unlikely that any car on the road will be able to accurately reproduce the same or consistent results.

As far as I know there are no standard tests for assessing fuel consumption when towing. Each magazine may have a preferred route or track system, but there may be significant differences due to specific elements of each test, and certainly none that would be able to demonstrate any significant difference in consumption caused by a load variance of 1Kg.

I am not sure that you could produce a performance indicator based on load increments, as it would almost certainly be a none linear relationship, in other words doubling the load would not necessarily produce half the performance or vice verca

There are far to many variables encountered in normal driving to be able to provide consistent high accuracy results, for example;
Temperature
Humidity
Wind speed and direction
Rain/snow/Ice
Road surface
Traffic conditions
Amount of fuel in your tank
How you accelerate
Condition/maintenance of the car (and trailer)
Tyre condition/pressures
and so on....

Mpg is best calculated over a large distances often including multiple journeys, by keeping records of how much fuel you put in, and records of mileage at start and finish. This will give you your most accurate results, but there is no guarantee that if you did the same journeys at other times, that you would get the same result. Consider doing monthly checks or even 3 6 or 12 months.

I am very sceptical when people claim they consistently get MPG's quoted to tenths of a mile, and even claimed results should be given a window of least +/-5% or about +/-2mpg or more.

 

[Lord Braykewynde]

To be honest I do load the car and caravan up with care but this is for safety reasons. If I was doing it to gain a couple of extra miles to the gallon I'd give up caravanning because I wouldn't want that worry to have a negative impact on my time away. I go to relax and enjoy myself. I understand it's a good thing to take care of the pennies these days but rather than worry about the mpg I'd rather cut down from full blown sites to CLs.
Since I've been driving I've yet to bother about working out the mpg on any car I've had so it's a bit late to start now

To consider your options see the postTips To Save FUEL

Heh! heh! heh!

 

[Willi-Wonti]

I thought about having my car chipped
It would increase my bhp from 160 to 200 bhp and improve my fuel consumption by 10%
After pondering about it, my car pulls my 1700kg van up the hill on the M5 from Gordano services to Weston at 60mph no sweat.
Towing & local driving (in Brum) I get between 22 / 25 mpg, so that is an improvement of 2.5 mpg. Considering I only drive about 7000 miles a year I will never get my money back

Oops just thought, I wonder how much my insurance would go up

 

[bopeep]

We are getting away from the point a bit, what I really asked is is it better to load the car or the caravan for better consumption.
I agree that it is for pleasure and should not penny pinch, but each trip I do is for long distances of many thousands of miles. I live in Spain and if I come to the UK then it is a minimum trip of 3,000 miles just to get there and back, my next trip is to Italy to tour and that will be even more miles.
I live next to the sea and I have the sun and the mountains, so I have to make each trip interesting, we do not have CLs or fields. So the odd 2 or 3 to the gallon makes a difference.
I just thought there might be some bods that had a bit more knowledge than me without getting too complicated.

 

[bopeep]

Duplicate Post

 

[ProfJohnL]

Hello again Bopeep,

I must got the wrong end of the stick from your first post. I apologise if it was not the information you were looking for.

I do not know for certain, but I believe it would make more sense to load the car in preference to the trailer for two main reasons.

The first reason is the cars suspension is usually more compliant and certainly better controlled than the caravans This means any load will be bounced around less. This is important because everytime you move an object it requires energy which in this case is supplied by the car engine. If the object is being bounced around like the caravan does it will sap more power. How much of a saving it makes is difficult to say, it may be so small that it cannot be detected amongst all the other factors such as those in my last post.

The second reason is not so much to do with efficiency but safety. It is always best to keep any trailer as light as possible. This will mean the tow vehicle has a better chance of keeping the trailer under proper control.

 

[Surfer]

Towing a caravan with the nose up will increase fuel consumption no matter if the car had most of the goods in it, however if the car's suspension because of the additonal weight levelled the caravan then i woudl imagine that consumption would improve.
We have decided against leasing an Orlando because of high fuel consumption and also because of the tow bar issue. Instead we have goen for a Vauxhall Insignia SE. Costs £72 more but better economy.

 

[ProfJohnL]

Hello Surfer,
Honestly this is not personal prod at you, but where have you got the idea or the information that towing with the nose up will increase fuel consumption? Perhapse you have found something that I am not aware of so please share your source.

I have considered the comment and provided the hitch height falls within the legally required 350 to 420 mm, I can find no reason to think that a nose up attitude will any worse than the equivelent nose down angle.

 

[Lutz]

The car's engine has got to do the same amount of work regardless of whether the payload is in the car or the caravan. The only conceivable difference could be in differences in rolling resistance of the caravan's tyres compared with those of the car. As rolling resistance is affected by load, this could have some effect, but I would imagine it to be so marginal that one would be unable to detect it among all the other factors over which one has no control and which have a much bigger effect.

 

[Dustydog]

Maybe Surfer does have a point.
When a car manufacturer designs the car's shape surely the drag coefficient is measured level , not nose up or down?

I remember some years ago Audi boasting their models achieved 0.30 Cd.
What do you think Lutz and Prof John?

 

[Lutz]

At the speeds encountered when towing a caravan (60mph max.) and considering the very small differences in angle involved between nose up or nose down, like John L, I cannot imagine that a nose up attitude is going to make any measurable difference. Hence his understandable query regarding the source of Surfer's information. Caravans are big boxes which don't behave aerodynamically like an aerofoil section. You mention a Cd of 0.30 (there are quite a number of cars today that better that), but the Cd of a caravan is probably in excess of 0.80. With that sort of drag, any change in attitude of the car is going to be even less noticeable.

 

[bopeep]

Hi Surfer.
I have a fiat doblo it can carry anything asked of it including a dining room suite and six chairs, it was time for something more luxurious but can still carry the same amount of goods, so I chose the orlando. I only test drove in briefly here in Spain and then it was only a manual, you do not know what they are like until you get some use out of it.
I have bought it and have to live with it, the tow bar issue has now gone to europe, as for the fuel consumption maybe nose up or nose down there might be a difference in consumption and when run in it may improve. I will have to dig deeper into my savings, hope you enjoy the Insignia.
My very first motorhome was a 37 ft american petrol and on a good day with the wind behind me I got 5 to the gallon,now I am moaning at 25 My best consumption solo was a Ford F350 with a 7.3 diesel pick up and I got 33 on a trip

 

[Steve L]

If you load a front wheel drive car heavy at the rear, you automatically raise the front and reduce the grip the drive wheels have. This will have a bearing on fuel economy.

Your driving style is by far the most adjustable factor to achieving a better fuel economy.

First off driving like a snail at 40 Mph doesn't mean great MPG. I accelerate fairly swiftly through the gears to get to my cruising speed and then maintain that in top gear (5th). Avoid heavy braking as often you over estimate the reduction and then have to accelerate more. Thus using fuel. When approaching roundabouts stay in as higher gear as possible while maintaining momentum. Look at the junction and the traffic flow and adjust your speed accordingly to allow you to enter the roundabout with the flow of traffic. Now change down to your exit gear (useually 3rd gear)and take your exit.

This is a difficult technique to explain in writing. But if you take a look at a main road roundabout near you, and watch how the Lorry drivers take the roundabout, you will soon pick up the idea.

Another tip is to look well ahead while driving and time your accelerations to coinside with down hill stretches to reduce the fuel used. But you must remember your towing and be aware of what speed your carvan does before becoming twitchy.

By being an anticipative driver and planning ahead, I can get a steady 37Mpg and even as much as 41Mpg out of my Rover 75 Diesel.

 

[Dustydog]

Steve
There must be something wrong with your Rover. A few days ago it was doing 58mpg!!

See your post below.
A typo perhaps

Wed, Mar 30 2011, 6:15PM
#8

steveinleo

Offline

Joined: 14 Mar 2005

At the moment, I am frightened to fill the tank as it would take all my weekly ESA payment to do so!!!!
By doing the math, I reckon £91-67p with diesel @ £1-38.9p/ltr.
On my solo average of 58Mpg, I get 838 miles.
Towing the van I get 37Mpg ish (depending on hills) so that would give me 535 miles per tank full.
Now I've had the scare of working out the cost of fuel, I'll retreat to putting my £50 a fortnight in and make it last.
Anybody got a bike for sale.

 

[bopeep]

Thanks for the driving lesson
going back to a previous thread about towball too high, I have heard from the boffins at Chevrolet, and they say it is correct to eu standards. This despite showing pictures of the height of the ball at 520 and pictures of the caravan in tow with the back end nearly touching the ground it is within tolerance.
So much for the chevrolet customer care, I am cast adrift with an unstable caravan because chevrolet customer care do not.
They have stopped answering my e-mails at technical support as well.
Where next I ask

 

[Lutz]

If you load a front wheel drive car heavy at the rear, you automatically raise the front and reduce the grip the drive wheels have. This will have a bearing on fuel economy.

My word! If you drive with the car so heavy at the rear that the front wheels are slipping through loss of grip, you should stop right away. An outfit as bad as that is plain unsafe quite, apart from the fact that you'll probably be exceeding the maximum permissible rear axle load.

I am cast adrift with an unstable caravan because chevrolet customer care do not.

A towball that is too high doesn't make the caravan any more unstable so long as the noseweight is set accordingly. If your caravan is unstable, then there are other reasons for it being so.

 

[ProfJohnL]

Hello Bopeep,

Just to be clear about the height of the tow ball. The measurment must be taken with the car in its loaded and ready to travel condition with the properly loaded caravan on the hitch. This means the ball is at its normal towing height and subject to a nose load. The EU tollerance for this on private cars is 350 to 420mm vertically from the spherical centre of the ball to horizontal ground for type approval.
Clearly some careful measurments need to be made, as you cannot see the ball hitch when a trailer is coupled.
If the Chevrolet was sold within the EU it should conform to the EU regulations.
If as you report the the ball height under loded conditions sits at 520mm, then that is significantly over the top limit the car is type approved for. There could be several reasons for this, and without being able to check the car personally I cannot tell you what the cause may be, but something is wrong.
If it turns out the cars is at fault, and Chevrolet are no longer answering your questions, you next port of call will be Trading Standards and possibley a solicitor to arrange to reject the car for being unfit for purpose, i.e. towing a caravan as the car does not conform to EU regulations as it should be for sale in the EU)
Do take note of my note below.

 

[Dustydog]

Hi Bopeep
Who fitted the towbar?

 

[Steve L]

I forgot to say "while towing the van" dusty, but then as I presumed we were talking about towing, I took it for granted.

I quite agree Lutz. I had a Renault 25 with a very soggy rear end. It looked like the nose weight was way out, but I never exceeded 75Kgs. I had some budget tyres on the car when I bought it. They were awfull as far as grip was concerned. So I very quickly got some Bridgestones fitted to rectify things. I also fitted a pair of doghnut spring assistors to the rear to stiffen it while towing.

Tyre choice and tyre pressure play an important part in fuel economy. If they are not inflated correctly or don't transfer torque to the road, they are not economical, let alone safe.

 

[Lutz]

I had a Renault 25 with a very soggy rear end. It looked like the nose weight was way out, but I never exceeded 75Kgs. I had some budget tyres on the car when I bought it. They were awfull as far as grip was concerned. So I very quickly got some Bridgestones fitted to rectify things. I also fitted a pair of doghnut spring assistors to the rear to stiffen it while towing.

Stiffening up the rear springs will level the car out, but it won't put any more load on the front wheels.