There are three devices now out there for saving fuel in the car.
Building a DIY Fuel-Saving Gadget, Cheap Tech Gets Big Results
Recently, I discussed a couple of high-tech gadgets for fuel economy, theScanGauge and the HKS CAMP2. Both plug into the OBD II port on your 1996-up vehicle to give you a real-time mileage readout. These devices are really great to help you fine-tune your driving style for the best fuel economy. And I've just started evaluating a third device, the PLX Kiwi, which is so consumer-oriented and so much fun to use, it might even help retrain the driving habits of all those nongearheads in your family.
I have a carchip device.
If you want to get more monitor and meter your car consider one of these devices.
The carchip is the cheapest device $100, but is not a real time feedback the way the other devices are.
Plus I only drive 3,000 miles a year. Recently added amazon.com prime and a kindle to my list of purchases, so I get out less and less. More time to think. :-)