Okay I forgot that they put the "Stealth" Performance as the default now. But it's interesting that with the upgrade package the range dropped from the past listed 310 miles to 299 miles, with the same 20" wheels.
There are tons of threads on this and discussions in articles online (use Google to find them). The old 310-mile number applied to the 20” Performance vehicle is from the 2018 Tesla Fremont test of the Performance with 18”. (Tesla did not test the 20” version and submit the results to the EPA.) This was allowed initially by the EPA in 2018 because the take rate of the 20” configuration is below 33%. That allows them to just use the 18” number.
Anyway, they are doing things right this time (though there is still some residual weirdness - they are using 2020 5-cycle results to obtain the two-cycle scalar for the 20” range, while not doing so for the 18” - for that, they are using same scalar from before, scaling the 2020 results by the scalar based on
2018 5-cycle results). It is apparent from this thread and others that that is the right thing to do, since few people appreciate the impact of tires and the aero wheels, and don’t understand the EPA rules. Tesla tested and calculated the range for all three vehicles appropriately configured, this year.
In 2020 Performance vehicles you can update the rated range between 299, 304, and 322 miles by selecting a different wheel configuration from the service menu (20”, 19”, 18”, respectively). All UI selections have the same available energy and actual range, assuming no actual hardware changes, of course. In all Model 3 vehicles (including 2018, 2019 vehicles), changing the wheel configuration in the menu changes the underlying assumptions of the trip planner, and will have an impact on its projections (highest consumption for 20”).