Oh.... and i wanted to add one thing.
The SUV i prefer better (obviously, for my needs) is the Subaru Forester. It is not so big (i don't like big ones!), but big enough to charge whatever i want. It doesn't have useless optionals and it is not so "beautiful" as some people like. But it has the best 4 wheel (or should i say "all-wheel"?) drive system you can expect.
It is also one of the few ones that comes out from the factory with the LPG system already installed, which means (although i don't know the details about it) that there is no waste of space for the tank.
The only problem is that, 4 years ago, when i bought the car, it costed over 35 thousands. Too much for my wallet.

here http://italianroots.blogspot.com/2008/04/alternatives.html is my blog post about my car.

@tychecat - 
Dick!
Your message made me think about an old RWD Alfa Romeo of some friend that i had to drive one day that was snowing (on a flat road). I didn't have no chains nor snow tires, so i was driving so slow that it would take the whole day to reach that friend in order to give him back the car. I didn't manage to drive on one curve. Wherever i would turn the wheel the car was proceeding straight. The car was old so that there wasn't any thing such as anti-skating system or anything. And it was a very heavy car. Anyway, the only thing i could do was just park the car on the side of the road and go to my friend by foot . But i was still a young guy!

Yes, i live in a hill area. I would better say in a mountain area. Just the 10 km i have to do from the office to home i have to climb 400meters on hairpin bends. Moreover my wife, my doggies and i like to go hike in the higher mountains when we can, so it often happens to go even further up. We also like to go where the tourists never would follow us, which, in the mountains, it often means that we have to drive on white roads. Yes, in the winter (but also in the good seasons) i can really appreciate the AWD system of my car.

I still believe that in the US cars are much cheaper than Europe (or atleast Italy). For example, the cheapest brand new Honda CR-V in italy is sold at 28K euros + APT. The same one in US is about 22K dollars (15.5K euros) + MSRP.
Not that i am complaining, but any time i think about this fact i end up concluding that price of goods are not anyway tied to their values. That's capitalism!

LPG. Uhm... I didn't know it was an American technology. On the opposite i thought it was an Italian one. The reason it had been distributed widely something like 35-40 years ago is that gasoline was really expensive compared to cost of life. Nowadays it is still very expensive, but general cost of life is grown much faster. I think in America gasoline at those times was much cheaper than over here. The effect of this is that LPG gas stations were already very common when that technology became complaint to the new safety restrictions and available without big inconvenient.
Although that fuel is much cheaper and more echological, and although the technology is really simple (actually it is the same engine of a normal gasoline engine), i believe that it is not the solution. LPG is still a fossyl extracted from petroleum, which means that it means that its cost is destined to grow with years, and its extraction is still controled by the petroleum cartel.
Hybrid engines are only a way to use less gasoline (or diesel), but it dosn't solve the problem.
I think the solution is in purely electic cars. But this technology is not effectively available. It is not acceptable that you have to stop every 100 km for 3-4 hours in order to recharge the batteries. Several times i drive to holiday destinations for 500-600km. What does it mean, that i have to spend over 20 hours only to recharge the batteries?
I am confident that this problem will be solved some way.
For example I read an idea of some american bugger to develop a standard battery model that could be easily and quickly replaced, also by an automatic machine. That way instead of stopping at the gas station one could simply stop at the "battery replacement station", and in few seconds you have the power for another run.
Yes, i believe that this is the solution being that it doesn't need to pollute (hoping that the energy is produced with clean sources). At the end this technology was invented and successfully applied over one century ago. If you think to the trams...!
Anyway, i believe that the definitive solution is just to reduce the use of cars, and in general of enregy sources. But i believe that this implies a total change of the society model. Easy step for a man but difficult step for humanity.

@tychecat - Dick... I looked online to Ford Explorer. That model is not sold in Italy. Instead there is a tiny crossover very popular over here by Ford (Kuga), which i don't like. Too fancy!

I like Explorer. It somehow looks like the RangeRover Freelander, but bigger.
I am always attracted in style of cars, as a cultural fact, although i tend to believe that a car is essencially a thing that has to move you from one place to another.
I like essencial, and obviously safety.

So, in the end of 40s-beginning of 50s LPG was already available in America? I am surprised! When i was a kid (say in the mid 70s) my father had a car with LPG system, but the distributors were not that common. So, i remember that dad built a pump to transfer LPG from liquid gas cylinders to the tank. That was illegal but much cheaper, being that cylinders were very common for cooking fires (methane was not yet widely distributed in those years in our area). I also remember that we put a huge LPG tank underneath the garden, for kitchen and heaters. Then after some years LPG for car traction became illegal because for safety problems. Then it became legal with some serious restrictions (LPG cars could not be parked indoor, they could not drive in the tunnels and they could not navigate on ferries. I believe the problem is that, differently from gasoline steam, LPG is heavier than air, so that leaks would cause invisible LPG clouds dangerous if air does not move and disperse it. Nowadays technology made LPG system much safer, more convenient and more echologic than all the other "reasonable" fuels for cars (hybrids still produce more pollution, methane has the problem of dimension and weight of the tank).

I read someplace an interesting solution for 4WD system with electric technology. Being that electric engines are much more little and lighter than traditional engines, somebody thought to put one electric engine for each wheel. I think this is the "columbus egg". It is really interesting because:
1) the engine could be put next to the wheel, so that there is no need for heavy and unefficient systems for distribution of power from the engine to the wheels
2) if the rotation speed of each wheel is governed by some electronics, there is no need for heavy differencial gear systems to transfer the power to the 4 wheels
3) being that at any time the speed of the wheels is given by the electronics, there is no need for anti-skate systems.
The result is that a 4wd SUV-Crossover would be much lighter, have more space, produce less pollution.
Moreover i believe that it would be even more power efficient. Usually suvs are supposed to drive in the mountains where it is very comfortable to have a larger band of mmmh.... "working torque" (sorry for the translation). In other words you can have power independently by the speed (of the engine).
Diesel cars have somehow this last characteristic. If the engine run slow or fast (within certain limits) the power is pretty much constant. Electric engines too.

I remember a discussion i made online with some nerd guy. We came to the conclusion that one problem (easily solved by differencial gears) is that it is really difficult to compute the exact speed rotation of each wheel when there is a curve. It strongly depends on the dynamic center of rotation of the car, which depends on the weight distribution inside the car. And the direction of weight force also depend on the acceleration (or deceleration) of the speed of the car. In other words the exact speed of each wheel can be computed only if we manage to weight the internal weights, and we give this value to an algorithm, along with the speed, the radius of the curve and tons of other variables.
If i well understood this is somehow what they made with the innovative 4wd system they put on the brand new Ferrari FF model.

(i apologize for the digression of my long comments)
Ciao
Dario

@tychecat - Dick,
Happy for your brand new toy Looks like you are satisfied of it.
You say "truck".... i thought in America they used to name cars with that word if they were that kind in Italy we call (with an english expression) "pick-up". Which means (i don't know if the expression we use is correct), that there is an "inside" part, for the driver and one or more passengers and an open back part.

I don't agree with what you say about the different speed of the wheels.
The differential gear doesn't need to compute the speed of each wheel (that's the really fascinating simplicity of that system!). Supposing that there is enough grip for all the 4 wheels, in the case of the curve obviously any wheel spins with a different speed, and the gear distributes the power so that any wheel has enough power to spin the right speed, but it is not giver which speed it is. Sure, if you have a differential gear, you can monitor the speed of each wheel, because the transmission made it available that power for them. But in a simulation (i. e. "before" you drive into a curve), it is hard to predict which will be the speed of each wheel.
Suppose you have only 2 wheels, one on your left and one on your right (like this toy, for example http://www.segway.it/). When you curve it is easy to guess which is the speed of each wheel:
Said "d" the distance between the wheels, and "r" the radius of the curve (in the center between the wheels), to drive an angle alpha radians, if the curve is on the right, the left wheels runs for a space even to (r+d/2)*alpha, the right one for (r-d/2)*alpha. The difference is d*alpha. The difference of speed, so, must take care that the left wheel, in the same time, has to make a space d*alpha more than the right one. Now, obviously the engine won't accelerate only the left wheel, but also decelerate the right one, so that the speed of the baricenter is about constant. Or maybe it is better than the forces (or the accelerations) in the baricenter keeps pulling about the same power... Anyway, it is easy to compute the difference of the speed among the two of them.
But if you have 4 wheels...?
The easy to compute problem for 2 wheels is given by the fact that it is easy to draw (and predict) the trajectory of each wheel. But with four?
Consider only the front wheels (which is the easier part, being tha they are the ones that turn, when you curve). The axis of the two wheels, first of all, are not aligned with the radius of the curve. So that the wheels are not perpendicular to that radius, as they should be, being that they have to follow the move direction. Which means that any individual wheel must have a "skating" rotation (perpendicular to the ground), but it is not given how much is that skating rotation of each wheel. It depends, i believe, on how much pressure there is on each wheel. Which depends on how it is distributed the weight into the car (if a fat guy like me is sitting on the right the weight is more on that wheel). Moreover the distribution of forces depends on how much is the speed (if the speed is faster and you turn left, the left wheel tends to pull up, the right to push down). It depends on the inclination of the road, on the responses of the suspensions, on the acceleration or deceleration. I believe also on how much sand or water there is on the road. And we are only considering the front wheels. If we consider the back wheels the thing is even worse. Obviously the center of rotation when you turn is not the center of the rear axe. Which means that what i called "skating" rotation (one wheel is dragged, and the other is pushed, so that they have to slide around the point where they touch the ground) is even less predictable. Now we have to see how is the distribution of weight not only between the two wheels, but also among the 2 front ones. We could also find out how the weights are distributed into the car (mmmmh.... dont know.... for example putting "scales" under the seats, in the trunk and whatever...) but then it is not even enough, because when a car is moving the weights are not directed through the center of the Earth, but it depends on the other forces involved. Also the module of the weights are not constant (if you have one kilo running at constant speed it will be one kilo, but if you are accelerating of 1g on a direction constant perpendicular, the module of the force is g*sqrt(2). Now we have several acceleration none of which is constant!!!
I believe we should study the dynamic distribution of weight onto the car. Difficult, but i believe we can make an algorithm to compute it automatically. The problem is that the variables envolved are not precisely computable. For example it depends on the efficiency of the suspensions, which depend on their usage. Also it depends on the grip of the tires, which depends on the usage of the tires, but also on the skating of the road....
Well... now i stop because my physics is not that good. My point is only that it is not that easy to compute.

One thing, just to explain my point. Think to the differential gear system. It works perfectly because it doesn't compute how much power it needs each wheel, but instead it is the wheels that ask for more or less power, and the differential gears only work to "satisfy" the need of each wheel the best it can.
In fact the differential gear system works fine only if there is enough grip on the 4 wheels, which is exactly the condition where you don't need a 4wd system.
But if there is only one wheel that doesn't have any grip at all, the differential gears don't know what to do. It's like if one wheel gets crazy and asks for infinite amount of power. To satisfy that need the system will give more and more power to that wheel and less and less to the other. Result, the car is stuck and one wheel turns at maximum speed. That's why they invented the anti-skate systems, which essencially pull the brake on the wheels to make the differential gears believe that that stupid wheel will be satisfied with less power. Kind of dumb system eh? You are using the breaks uselessly to lower the speed of one wheel which speed is useless, in that way you are consuming the breaks, and you are pushing the engine for no reason. But, who cares? It works fine, and hopefully when the car moves that mad wheel will have eventually more grip for its normal job.
Well, if you don't have a differencial gears system available, you cannot use those tricks.

@tychecat - uhm.... <20MPG?!?.... rapid calculation.... less than 8.5km per liter.... that's a lot of gasoline!

Dick, i believe that the problem of different speed of wheels applied to a vehicle like mars rover would be much easier than if applied to a regular car.
I believe that mars rover was 4wd, but also, if i well remember, the rear wheels turn on a curve, and also that the axes are turning around the center of the axes, so that the axes themselves are always oriented on the radius of the curve, which makes it easy to compute the difference of speed as in the case of the 2 wheels vehicle i was speaking about in one previous message.
I don't know if there is a differential gear or not (or if there is 3 of them as it is supposed to be in a 4wd car). Anyway, i believe that there should be some sort of anti-skate system, because i guess that there would be a lot of occasions in which the vehicle would have one or more wheels without any grip (it's not a road).
If i was the one that made the project of that vehicle i would simply not put any differential gear nor other difficult (and heavy) system on it, and i would make the wheel move the same speed always. Infact i believe that in Mars the vehicle would have never found any tyreman to replace usured tyres, but i also guess he would never find also a policeman to give him a ticket for having usured tyres
The problem solved with differential gear is that if the tyres slide on the road ground the car has less stability, and the forces involved would give the car an unpredictable behavior. Moreover the tyres would be consumed in less time.
But in the case of the mars rover, i think the speed was less than one meter per hour or something, which make the acceleration due to the movements and the curves negligeable with respect to the gravity of mars. Maybe the tyres would be more consumed (although i guess the ground wouldn't be hard like the asphalt - i think more similar to sand), but they had to endure only few days no?
With a normal car the problem is to find the right speed of the wheels, when the car is moving, when it is making a curve, in three dimensions (it's not said that the curve is flat), and the system should continue to work also if the weights on the car are not evenly distributed, and maybe they are moving. The problem is to make so that the tyres would keep spinning the speed needed so that they don't slide on the ground. That problem is efficiently solved by differential gear, but WITHOUT computing the real speed of each tyre.
If we are able to compute the speed of each wheel, given the trajectory we want to give to the car (which is corrected at any time), if we give the wheels those speeds, we are sure that there won't be any skate problem that can be solved correcting the speed theirselves, because that is the correct speed. So we won't even need any anti-skate system, and we can get rid of such a primitive (and heavy) system like differential gears.
Actually that system was invented because the traditional gasoline motor is heavy and big, so it is more useful to have only one of them into the car and transmit the movement to the 4 wheels. Being that an electric motor is much smaller (probably the motor itself is smaller and lighter than the wheel it has to move), it looks more convenient to have 4 motors, one for each wheel. The really heavy and bulky thing in a system like that is the battery. You can also have one big battery for the 4 motors (the energy is distributed with simple and light copper cables. Believe me, the real problem in a system like that is to compute the right speed of each wheels. Right, it could be computed by a small computer like your laptop. It could, if there was such an algorithm that know how to. And if there are the correct inputs.

Think you have a truck like yours, for example. You are driving it alone. Prbably you will find it a little understeering. Which means that you have to turn the wheel a little more than what you think you need to keep staying on the road while you curve, especially if you are driving fast.
If you are charging a heavy weight on the back, still you will have an understeering feeling. Even worse if you are pulling your boat on a cart.
If, instead you are driving with mr. Fat sitting on the front (and nobody in the back no baggage...), and also during your curve you are quickly slowing down, you will find your car more oversteering.
That's because the natural trajectory of the car heavily depend on the kinematic distribution of weights onto the car. Or, in other words, where is the baricenter of the car at any instance, and which direction that baricenter is attracted. That depends on several factors that in a normal car are not sensed, like how much weight there is on the car, how it is distributed with respect to its center of rotation, how usured are the suspensions, how much dynamic grip there is available on the road...)
And those problems actually are the ones that are very involved in a 4wd car (if you make some offroad). Suspensions are subject to stress, the ground grip is not well defined, the weights keep moving on the cars (at any hole of the path).

I believe to solve this problem we should first of all detect which are the variables involved. And then we should find a system to detect instantly those variables, and only then we can find a correct algorithm to compute the theoretical speed of each wheel.