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After watching a TV show about diesel locomotive, I learned that the diesel is actually run by electric motors and diesel fuels the generators.

Why don't manufacturers build an electric car that is charged by some small generator that is gas or diesel fueled. The Prius/Honda hybreds are sort of like that except the gas engine powers the car as well as the electric motor powering the car. I'd think that you would only need some small gas engine generator that could supply all the electric an electric motor would need to run an engine for a car.

I have a 6 hp briggs and stratton powered generator that puts out 6500 watts for when I have power outages. I don't think the 6 hp generator would used that much gas (supposedly 10 hours of power on 6 gallons of gas). If the car could go 60 mph for 10 hours using 6 gallons, that works out to 100 mpg.

What am I not seeing with this logic?

The most efficient way to turn gas/diesel into motion is to convert it directly into mechanical energy that goes to the wheels. Using it to run a generator or charge a battery involves more conversion losses.

Hybrid benefit comes from the fact that cars have more power than usually needed, so you use the engine hard for a short while, then shut it off. BEV's have the advantage of taking power from the grid at much greater efficiency than our car engines. At the end of AER, a generator is a way to extend range. This is the Volt idea, basically.

Your generator may lack emissions controls. It would need to run the AC, brakes, steering, etc. Apparently when you meet all these demands, the mpg is not as high as you imagine it would be.

Even a Prius uses more than 6hp to go 60mph, I think. Seems like it takes 12 hp to go 50ish in good conditions. I've seen threads here, maybe dealing with shm...

As ksstathead said, this is the concept behind the Chevy Volt, well sans diesel. Perhaps if they are successful, others will move towards this idea, which I also think shows a lot of promise.

One bit of logic you're missing is that 6 hp cannot produce
6.5 kilowatts. One or the other number is off.
.
_H*

Conversion losses, as stated, are a big issue. Another consideration is that when the vehicle (e.g, the Volt) is running on electric power and the generator set is not running, it is lugging around the weight of the generator, and that weight reduces efficiency. This becomes more important for lighter vehicles.

So it might be more efficient, depending on how one weights the relative "value" of gas (or diesel) vs electric power, to have an electric-only vehicle for normal use and have (or rent?) a hybrid (current type or Volt), a diesel, or a small conventional gas vehicle for longer trips only.

Another thought is that if speeds were reduced, vehicles could be made lighter by designing them for slower crashes only. This alone would increase FE to some extent. In this case the speed limits would be based more on the crashworthiness of the vehicles than on the probability of crashing. "Yes you can probably negotiate this road at 75mph without crashing, but the car is built for a <55mph crash, so if you crash at 75 you're probably toast."