If the advertised range on the 2018 plug is 31 miles, and you can document that you're not seeing anything approaching that, then you need to bring the issue to your dealer and escalate as needed.

Your range is only going to decrease once the winter sets in on you.

 

Agree with ace10. I have a 2016 S e hybrid. I get readings of 13-16 in summer but actually get around 15-19 miles of range. In winter, I get readings of 11-14 and true range of 11-15 miles. In summer, even if the charge reading says 12, I go a few miles and it still says 12 - almost as if it is recalibrating on the fly. Definitely a decreased range in winter.

 

I get 14 miles.
If I drive 60/70 on highway
I get 16 if I cruise at 40/45
I get 17 ish if no AC system and 18 if no AC/radio in use and so on
I may get 20 miles if i calculate every meter of asphalt ... gliding etc...

 

There's a lot more about this at the Rennlist online discussion forum, where there are a lot of 2018 Panamera E-Hybrid owners involved in discussions. Nobody gets 31 miles, essentially -- though I could get close to that in ideal conditions (no wind, going 25-30 mph, long, straight highway with no cars and no traffic lights, etc.). I have gotten close to 26 miles in my daily commuting in all-electric mode, with hills and stop/go traffic. Generally in warm (not hot) weather, I'm getting 21-23 miles, with some fast driving for short stretches on open interstate highways (it's hard not to do some fast driving in a Panamera when you get the chance). Most other E-Hybrid Panamera owners say the same thing -- lots of consistency between cars. The onboard computer has given an estimated range as high as 31 miles on a full charge in my car, but generally it will say 28-30 miles (with the air conditioner off; with it on, it'll read as 3-4 miles less, and that's actually closer to reality anyway).

So, in a nutshell, you could get 31 miles probably if you had perfect conditions and didn't drive fast and have flat terrain. But the E-Hybrid in 2018 form gets way better range than the older versions of the Panamera S E-Hybrid, which I'd never consider (and I have driven them).