I learned very quickly I couldn't trust the ol GOM. My commute involves driving entirely downhill, and returning all uphill - and that's not including the searing heat and (occasional) cold. The GOM varied too widely to be trusted, which is why I ended up getting Torque Pro, OBD2 port and cheap Android phone. It's been much more accurate.
This is the one I have: https://www.amazon.com/gp/product/B01BY2CK32/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 Torque Pro is required in order to use the Bolt PIDs to access the data points you need. It's Android only, so I purchased a used phone from the Walmart phone store. One of the forums on the MyChevySparkForum website has a Youtube video how to install the PIDs on an Android phone - sorry can't find the link right now.
Another app - Car Scanner ELM OBD2 - works on iOS and Android. No need to install external PIDs, simply select Chevrolet Bolt (yes, Spark EV works with Bolt profile). You can also import custom PIDs to Car Scanner, if needed. iOS requires Elm327 Bluetooth 4.0 or Wifi adapter.