Fuel economy question

You would be towing the same weight, regardless of where you put it. 

The two factors that will affect the mpg are weight and drag.

I would have thought the better balanced your set up is the better your fuel consumption. I would not have thought it would matter where the weight was as long as the optimum towing balance was achieved. Seem logical to me, no idea if I am correct.

It might not make much difference but every correction that your car has to make to the direction of travel (up/down or side-to-side) of your caravan will consume energy and have an adverse effect on mpg. So you do need to consider where you put your weight. Carry as much weight as you can in the car. Keep weight in the van as low and near to the van axle as possible, while maintaining the noseweight at maximum. 

I think the biggest factor that affects consumption is wind resistance. Polish the van and, if you are driving a convertible, shave your head. 

So maybe there is a marginal gain by weighing your car down and ‘hiding’ the wheels…

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I've talked with a physics professor today, and he states that the load should be carried in the car as near to the drive staft as possible for best economy due to resistance v load theory...he did draw me an equation, but I got lost after the words "let me show you"....

When you tie a box with the aerodynamics of a house brick on the back of any car any decent fuel consumption it had is out the window and going uphill or into the wind or both will make it even worse.

peter.

Agree with what people have already said:

It should make very little difference where you put the weight. weight only really affects frictional losses from the tyres and bearings etc (assuming a set weight). Obviouisly the heavier the total outfit, the more energy will be needed in any elevation change (potential energy).  

What ever is the most stable and most balance configuration will give you the least losses (marginal gain).

But these pale into insignificance against the air resistance losses - drag from the van, which you can do little about!

Remember that drag is equal to half the density x velocity squared x area x drag coefficient. The important bit is the velocity squared, so the drag gets much much more as the speed increases - doubling your speed quadruples the drag!

And the power needed increases as a cube of velocity doubling your speed, means 4x the drag and 8x the power needed and power comes from burning fuel! 

If you are worried about fuel consumption, slow down a bit, it will make a significant difference!

(but will get you parped and bring us caravaners into disrepute!).

 

With a good load in the back of my car (2.0TDi estate 4x4) awning poles, BBQ etc., etc. and caravan loaded also 2 bikes on the car roof all well within my weight / load limits of course. German / Czech motorways at 50mph using Ultimate diesel, not complaining at 37mpg. But then at 40mph, for safe towing, same load in a head on gale force wind heading for Dunkirk to catch the ferry, it did drop to just under 30mpg.