Are you reporting your guess-o-meter's number or the number of miles you actually get when you drive on EV until the engine kicks in? You can use the climate control screen to turn off the AC, but it doesn't affect EV range nearly as much as the resistive heater. When the heat kicks in, your range will plummet.
Did you ever use the heater on the Volt? Did the heater affect the range on the Volt? Is the Volt range correct, or a Guess?
I can't see how it is ever possible for an EV range meter to be "correct". EV range is entirely dependent on the driving scenario and terrain, and the vehicle cannot possibly know what the driver's intent is. Therefore, a "Guess-o-meter" is the best you will ever have on any vehicle. The Volt doesn't have a crystal ball either.
Did the Volt actually deliver 52 miles of EV range every time, or does the gauge just show 52 miles after every charge? You need to turn the A/C off by pressing the “Off” button on the climate screen. The manual will provide additional information on the controls and features of the vehicle. I’d recommend that you have a dealer perform a battery capacity test on the traction battery. A healthy battery should be in the neighborhood of 54Ah. What you do not want is a CCA report on the 12V battery. Until you get that report, we’re all just speculating on your driving habits and climate control settings and how that may be impacting the EV range estimate. No, we do not all see a 38 mile range estimate, in warm climates. That would be very good range in cold temperatures, say below 45-50F.
You need to select "OFF, and you also need to dial the temperatures all the way down (it will say "LO"), otherwise it is possible for the heat to kick on.
Just drive the mileage will change as you drive. I just went on a day trip of 230 miles. I had 58 EV when I left. Filed up and drove back - 83 on it when I got home. Down a pass and then on flat land. The EV is just an guess calculated on your last few drives.
If it helps, I have a 2019 Volt and a 2018 Clarity. My wife drives the Volt and her range is usually in the 60s during the summer. I drive the Clarity and my range on my GOM is usually 10 miles less than what is shown on the Volt GOM. Some is that we just drive differently, some is the difference in the two cars.