I learned about this product on the http://hypermiling.com website.  Although I consider myself to be a fuel efficient driver, typically getting better than the EPA stated mileage on most cars and trucks, I felt that having a real time MPG meter would help.  I could also conduct experiments to see what difference various accessories makes on my fuel economy.  This product does that and even more!

Basic installation is easy. Just plug the provided cable into the ODBII port on your car, located under the dash near the steering wheel and the other end into the ScanGaugeII unit.  The ScanGaugeII has a jack on the back as well as the side, so you can customize your installation anyway you want. You can set the backlight to be dim or bright and select the color from 7 presets or set up one of 64 possible custom colors. I used the supplied Velco strips to attach it to the dashboard, out of the way, but still where I could glance at it easily.  Once plugged in, turn the key on.  The ScanGaugeII figures out what protocol the car uses and in less than a minute is ready for use.  In the rare occasions in which the ScanGaugeII can't figure out if your car uses PCM, ISO or whatever, the manual has instructions on how to set the protocol manually.

From the main menu, the three basic uses of the device are available. Scan, Gauge and Trip.  Scan allows you to find out why the "Check Engine" light is on.  Sometimes the cause is as simple as forgetting to put the gas cap back on.  Once the problem is corrected, you can clear the diagnostic trouble codes (DTCs) turning off the "Check Engine" light.  The only downside to this particular scan gauge is that only the raw DTC is displayed, not the meaning.  So if you get a display of "P1440" on your 1999 Ford Ranger, you have to look in the truck service manual or do a search on line to find out it means "EVAP System Leak Detected, Small Leak", which could be caused by a loose fitting gas cap.  Fancier dedicated diagnostic scan tools will display the meaning of the standard codes, but they won't do other things that Scangauge II does.

For daily driving, the Gauge menu is selected.  The four factory default values displayed are engine RPM, Speed, MPG and water temp. But you can select any four gauges from this list in addition to the above choices. Fuel system loop status (open or closed), Fuel cost per mile driven, Intake air temp, Fuel Pressure, Gallons per Hour, Ignition Timing, Manifold Absolute Pressure, Throttle Position and Battery Voltage. Note that all items may not be available on all cars. But there are some items unique to some cars or trucks that can be displayed. For example, the Ford Ranger with Automatic transmission outputs a reading of the "Slip", that is the ratio of the input to the output of the torque converter, with a value ranging from 0 (car is stopped with engine running, foot on the brake and transmission in "Drive") to values slightly greater than 1 (coasting downhill). These vehicle specific items can be programmed using the XGAUGE feature using codes listed at the ScanGaugeII website.

For the most accurate results, the unit needs to be calibrated first as explained in the manual.  Once that is done I found that the Tank MPG displayed by ScanGaugeII agrees with the traditional method of measuring miles per gallon.  But the most informative display is the real time MPG.  I found things about my truck with an automatic transmission that I didn't realize.  For example when going up a steep hill, I get better economy by taking it out of overdrive, even if the engine RPM is higher, because there is less torque converter slip but on gentle hills it's best to leave the overdrive on all the time.  When descending a hill it's often best to downshift or at least turn off overdrive, as that will rev the engine high enough to cut fuel consumption to zero, as the engine control unit detects that there is no load on the engine, so no need to consume fuel (the MPG will read 9999 in that case).  The most profound difference in real time MPG is the nature of the terrain, it takes a lot more fuel (around 9 MPG) to go up a hill in my truck then to drive on a level road at 45 MPH(around 20 MPG) or descend (35 to infinite MPG). So if you have a choice pick the flattest route.

Upon conclusion of your day, you can review the Trip menu.  The trip menu will give you information about the current trip, all trips for today, the previous day and the use since the last fill up.  For each of these items, the maximum speed, maximum water temp, max RPM, average speed, average fuel economy, trip miles, trip elapsed time, trip fuel used and trip fuel cost can be displayed.  The "tank" information does not display maximums, but shows fuel remaining, fuel used since last fill, estimated distance remaining before empty and time driven since last fill.  I find the "cost of trip" to be most useful, I can now bill clients for the exact fuel cost of a trip to their site.

When you first start using ScanGaugeII, you'll want to make sure that the manual is in the glove box, you'll be referring to it a lot, and you'll want to pull aside after your first few fill ups to do the calibration and program in the fuel cost per gallon without annoying other people waiting to use the fuel pump. But once you get used to the ScanGaugeII it's easy to record the cost per gallon paid and make any minor corrections to the amount of gas purchased.

I've owned this unit for two months and the only problem I had with it was when the battery terminals were loose on the truck and it would not start.  The low voltage while trying to crank "scrambled" the memory on the unit and I had to reprogram all my custom settings except for the XGAUGE customization, which oddly enough survived. Fortunately I had the forsight to write down all my custom settings and store them with the manual.  This will also be needed when I move the ScanGaugeII to my 4 cylinder RAV-4 this spring, the initial calibration for my 6 cylinder Ranger won't be correct. It would be nice if the ScanGaugeII had a means for storing calibration and setup info for more than one car.  It would also be nice if the data could be downloaded to another computer for further analysis.

UPDATE:  I now have some experience with using the ScanGaugeII on the Toyota RAV4.  The only difference is that the real time data is not quite real time. It displays what's happening about 3-5 seconds after it happens.  The response is faster on my Ford Ranger. This is probably due to the nature of the ECU on the Toyota, rather than the ScanGaugeII.

Recommended: Yes