I just bought a RX 400h hybrid vehicle from Lexus of Clear Lake.

This was the first hybrid vehicle sold by the dealership. I paid the sticker price for it; the only extra option was heated seats that I had to buy because all the initial vehicles arriving had it.

I drive about 120 miles per day: 70 miles at about 65-70 mph along the beltway around Houston and the remaining city miles with stop-and-go conditions.

I have been averaging about 23 mpg highway and about 28 mpg city. In my subdivision or when I am cruising around work at NASA Johnson Space Center (speed limit of 25 mph), I end up driving in EV mode and thus save gobs of fuel.

Initially, I was very disappointed by the mileage obtained (EPA 29 highway, 31 city), but then I learned the techniques to coax the beast to drive with more electric power and rely less on gas at low speeds. It is still a bit of a struggle, but I prefer to look at it as a challenge.

What is frustrating is that I have worked extensively in Regenerative Braking Systems in my past life in the auto industry and know how to fine tune the vehicle. Everyday I wish I could lay my hands on the software that controls the CVT and tune the control decisions - particularly when the gas engine kicks in. This vehicle is not tuned to save fuel. Lexus could, in my opinion have done a better job to get it to kick into gas mode a little later in the acceleration. Lexus doesn't seem to exploit the high starting torque of the electric motor, but depends on the gasoline engine revvving up to provide that kick off.

I have also noticed that with frequent accelerations to 40 mph followed by regenerative braking (typical suburban driving), the batteries charge up to almost 100%. But, they are reluctant to give up their charge by indulging in a little more electric only driving.

One needs to be very gentle on the gas pedal (frustrating drivers behind you) to keep it in electric-only phases during acceleration.

In summary, I would think that they could optimize/improve the system by:

1. Delay kicking in the gas engine during acceleration. Allow the motors to do their job as long as possible. Allow the motors to impart more torque and better participate in acceleration and use up some of the stored energy. If need be, provide a switch that would allow the driver to select between a fuel saving mode and a performance mode. I am sure the CVT programming can be done to accomodate this.

2. If the fear is that batteries could drain to zero resulting in starting trouble, my suggestion is to provide a simple plug point access to the batteries - one may charge them using household 110V AC. This way when we return from a long vacation, we could plug this in for an hour or so and fully charge the batteries. The operating manual that comes with the car does scare us that if the vehicle is left unused for a month or so, the batteries may discharge completely and that we need to call Lexus to get a special jump start. Jump starting from household electricity (that all garages have), would save us from that anxiety.

Besides the above 2 peeves, it handles like a beauty.

My other vehicles are a BMW X5 3.0 liter and a Lexus LS400. The RX 400h easily out accelerates both the vehicles. The ride is almost as good as the LS400. The handling is also good - though not as good as the BMW. The RX 400h can out-accelerate the BMW and the LS400 in a 0 to 60 sprint.

It was definitely a pleasant moment when I stopped by the gas pump for my first refill and found that with just $25 (@ $2 per gal 87 octane) the tank filled up and it lasted me about 320 miles. Compare this to either my LS400 or BMW, which need the more expensive 92 octane and their 17-19 mpg thirst - resulting in about $40 per fill up over the same distance.

During driving, you never hear/feel any changes in gears as the CVT (continuously variable transmission) smoothly operates. With the CVT, gone are the days when you could hear the engine roar change and the little jerk as it changes gears.

If you want to buy this vehicle just to save money on gas - think again! You probably will need to drive over 120,000 miles before the fuel saving will catch up with the higher initial payment of about $9000. However, if you are the type who gets a high acquiring new technology, it definitely will satisfy that urge. You will feel good about all the greenhouse gasses that you are not pumping into the environment without sacrificing performance.

The greatest benefit that I seem to have derived driving the RX400h is that it has compelled me to be a safer driver:

1. I now come to a full halt at stop signs (without the guilt of wasting kinetic energy as heat energy in the brakes).
2. I do not brake hard (instead brake using the regenerative system).
3. I do not hit the gas pedal when the light turns green (instead gently accelerate trying to use the electric motor only).

Looking forward to an exciting next few years. And, also for any software updates to my car's computer that Lexus may come up with. I hope they consider the above suggestions.