Ultra-gauge
 

Having some instrumentation that works is great. The onboard computer is pretty optimistic in comparison. Makes you wonder how many people ACTUALLY trust the onboard gauge.

Makes you wonder how many use it and if it changes their driving style.

...that's the problem I'm having with noobies over on the CruzeTalk website--they're all "believing" the numbers from the Drivers Information Center (DIC...how appropriately named?!?!) rather than first verifying those numbers against a "one-click" tank-fillup.

...by the numbers I'm tracking on the wife's Cruze, the ECU is consistently under calculating the fuel consumption GALS by a rather consistent 5-10%, which means all the DIC dispaly MPG values are likewise 5-10% too optimistic.

This tank was the second with the UG and it reported 37.3 and actual was 37.33 mpg.
Awesome!

...both the SG and UG, once calibrated, seem to give far more accurate results than just about any of the OEM built-in dashboard display units...at least that's been my experience.

...FYI, even though you've calibrated the unit now, be aware that when the gas companies switch over from "winter" blend to "summer" blend, the meter accuracy will likely change...and it'll change whenever they change the amount of ethanol alcohol in the blend, such as from the current 10% (E10) to the new EPA limit of 15% (E15).

I will also confirm a recalibration for winter mix. I had to adjust my UG for my Subaru at the end of December, it seems to be slightly optimistic, but thats okay. Even in an over-calibrated situation, I can still tell I'm doing good or bad for the tank.

I also have issues with my Subaru for extreme colds (PA extremes lol). My mileage always dips if we're down near zero or below. The Subaru runs extremely rich when cold, so the UG will be off for me.

Is there a simple way to calibrate the ultragauge? Similar to how the scangauge is calibrated?

UltraGauge instructions.
 

Never had a scangauge but here is an excerpt from the ultragauge manual.

Calibrate MPG/Fuel
MENU  Vehicle Setup ..  Calibration..  Calibrate MPG/Fuel
This calibration is used to fine-tune UltraGauge to accurately measure fuel usage. This calibration is critical, especially for vehicles
which use a MAP sensor, diesels and alternative fuels.
 For vehicles that use a MAP sensor*, see the menu section on Adaptive Volumetric Efficiency before proceeding.
 Prior to this calibration, consider performing the distance calibration. See the section: Calibrate Distance
The gauges that depend on fuel usage will not be accurate until this calibration is complete. To perform calibration, please follow
these steps.
1. Fill up the fuel tank. Once filled, press and hold the UP key to cause UltraGauge to recognize the fill-up
Zero the Average MPG. MENU  Gauges  Zero Ave MPG, G/H.
2.
At the next fuel fill-up, note the number of gallons used (pumped). Select MENU  Vehicle Setup..  Calibration.. 
3.
Calibrate MPG/Fuel and enter the fuel used. Press MENU when complete to set and save the calibration. Use the same
Gas station and pump for best results. Alternatively, record and add the actually gallons used over several fill-ups to
improve accuracy.
4. The Calibration factor will be displayed at the bottom of the screen.
Congratulations, you have successfully calibrated UltraGauge to your vehicle.
Make note of the calibration factor. If you should ever need to clear your configuration, the calibration factor can be used directly
to set the calibration. Simply jump to step #5 and increase or decrease the reported gallons until the calibration factor matches.
* To determine if your vehicle has a MAF sensor, access the menu; MENU  UltraGauge Setup..  Version. This will display
MPG sensor: MAP, MAF or None


Manual may be downloaded here:
UltraGauge Support

I advise reading and understanding the set up instructions first and then not plugging up the UG until filling up. You can then keep tabs on calibration as you go through the tank.
On my first tank I checked calibration after each 100 miles and then upon filling up again the UG reported I used 16.112 gallons and I actually used 16.351. The second tank needed no touch up on the distance calibration and the fuel reported use was spot on.

The fuel use report since first installing is a running tally...
First tank report was 16.112 (calibration tank) actual was 16.351
Second tank report was 31.659 which is the first tank of 16.351 and the second tank of 15.308. It was dead on accurate of the amount of fuel used.

Bharvey how long from when you ordered you ultragauage did you get it?