When I release the throttle, the revs don't come down very fast. Is this by design due to the automatic tranny? My other car has manual tranny, and it decelerates quickly, almost as fast as I release my pedal. It make the car a bit jumpy, but I prefer that to a slow deceleration which seems to be a waste of fuel if you ask me.

 

In a manual transmission car, when you let off the gas the gears are still fully engaged. I'm not completely sure how an auto tranny works when the gas is let off but I think... i think,thatthe torque converter disengageswhich puts the car in a"Neutral" state causing the car to coast further. I could be wrong, but that's what I think.
All of my automatic cars don't slow down as fast as a manual.

 

I've become more aware of how my car operates over the past couple of months, mainly in an attempt to increase my mpg. I've noticed the same thing, axelm. From 0~38mph the rpm won't drop off much at all when I let off the throttle. This has to do with the fact that it has a torque convertor and that it doesn'tlock until 40+mph. Above that speed it locks and increases the transmissions efficiency. Letting off the throttle above 40 I can see a drop in rpm more noticeable, but always much higher than normal idle. I was out driving today with my Scan Gauge and actually noticed a phenomenon known as "fuel cut" when I got off the throttle and coasted. I verified it with the various gauges it monitors. So its not burning nearly as much fuel as you might imagine.