~30% MPG drop after better driving habits

[MetroMPG]

1) If you're serious about saving fuel, you need better feedback than the fuel gauge. As others have said, get a ScanGauge or Ultragauge. With the amount of fuel your truck uses, it'll pay for itself in no time.

2) I'm skeptical anyway. My experience is: people worry way too much about acceleration technique. If you're not pulsing & gliding, accel. style will have a small impact on your overall tank mileage. FAR more important is use of the brakes (sub/ex/urban driving obviously), and it sounds like you're headed in the right direction there.

I'd suspect filling technique, whether your routes/usage is identical to the tanks you're comparing, and whether or not you've actually re-filled the tank yet (it's mostly useless to guess based on the needle!).

[pdizzleccc]

Is your info from the fuel gauge or on fill up? The reason I ask is those vehicles are notorious for having their sending unit fail, causing bad readings your gauge (put 2 chevy pumps in my dads 2000.) I remember if you are careful with it those rigs are pretty easy to get the T.C. to lock up, that's where I would want to spend most of my time driving. Word of caution I know some have T.C. lockup switches in their rigs, while this is helpful, it can also cause damage if not used properly and the transmission in those truck can be problematic at higher mileage.

[Aero]

I would never trade a few miles per gallon for a few broken bones in an accident...