BrevardBioDiesel Blog

(This is a follow-up review to our first look at the ScanGauge)
Before leaving for the Elsbett Workshop, I stopped by Jay's place to borrow his Jetta Maintenance Manual, and he asked if I would like to borrow his new ScanGauge also. Sure! Sounds like a good chance to gather some fuel economy statistics.

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Jay gave me Velcro strips to attach it to the steering column, but that seemed to block part of the instrument panel view, so I just put it up on the dash. Installation took 15 seconds - just plug it into the diagnostic connector and tuck the wire out of the way.

By the time I had traveled a few miles the next morning, it was obvious that something was amiss. Scan Gauge registered about 25MPG, even on I95! I had never measured MPG carefully, but had twice driven 750 miles on a fill-up, which must be around 50MPG. I checked with Jay by cell phone and we deduced that there is a fill-up calibration that determines the MPG calculations for each type of vehicle in which the Scan Gauge is installed.

So I punched a few buttons and did a "fake" fill-up. In normal use, each time you fill the tank, you calibrate Scan Gauge so that the amount of fuel it thinks you used since the last fill-up matches the amount you just put in. To do this, you adjust a scale factor by pressing the "<" or ">" buttons. With each fill-up, the difference between calculated and actual fuel quantity theoretically gets smaller, and the mileage calculation gets more accurate. With my "fake" fill-up, I just changed the scale factor from 100% to 50%, since it was registering about half the fuel economy I expected.

Presto! Now the MPG registered almost 60MPG. This seemed too high, but I figured that on the next fill-up the calibration would be more accurate. During the next week, I filled up three times and converged on a scale factor of 35%.

MPG results for 2005 Jetta TDI wagon with manual transmission (with air conditioner off and running nearly 100% petroleum diesel - [future testing will compare with BioDiesel]):
I-95 cruise control @ 70MPH ~ 47MPG
I-95 cruise control @ 60MPH ~ 56MPG
Local in light traffic up to 45MPH ~ 35-40MPG
Local in heavier stop & go traffic ~ 25-30MPG

It's a clever device, easy to install and use, and it can report a large number of parameters for each fill-up, each day, each trip, or each trip segment. I found the display easy to read in daylight, but difficult at night in comparison with the blue displays in the Jetta instrument panel.

Scan Gauge won't win any awards for style or aesthetics - the packaging is just as logical as the user interface - probably both designed by the same engineer!

Thumbs Up!

Jim Woodfin