I just put on Conti Pure Contact LS in 245/40-19 on a new wheel that has 10 mm more offset (pokes out 10 mm further). These are Eco rated tires with a 700 treadwear and so far I've seen at least a 10-12% drop in efficiency versus the 18" Aero wheels with covers. It's about 40-45 degrees here, and I have to absolutely baby the car to get below 290 wh/hrs. It's quite surprising that this minor change creates such a difference and it makes clear that Tesla spent a ton of time optimizing the efficiency of the stock 18 wheel/tire package.