RPM's when truck in neutral

[rickstrk]

With the price of diesel at $4.30 in the NW I thought I would try to save a gallon. I have been shifting in to neutral going down hill and have found that the RPM's don't drop to 600. Matter of fact it starts a 1000 and goes up as I pick up speed. :confused:
On a side question from another post I didn't get a response is my wipers will hesitate every so often.:(

[DmaxMaverick]

You will burn more fuel going downhill in neutral, than on compression. This isn't a gasser with a carburetor. When on compression (engine RPM higher than the PCM command RPM), it will go to zero fuel input, or only enough fuel to maintain command RPM. When in neutral, it will use enough fuel to keep the engine running at the commanded RPM. When rolling, the PCM will command the RPM within a window, according the ground speed and gear the tranny is in, or would/should be in.