Edit: Results start here: P85D vs. P85 Efficiency Testing - Page 6 Edit: Data entry here: P85 vs P85D Efficiency Data - Google Sheets So, the details around my upcoming efficiency head-to-head have been somewhat scattered around the forum in various threads. Tomorrow is looking like it is going to be the day to actually do the test since it should finally be clear all day weather wise. High temp is predicted to be a bit low, low 50s, but this shouldn't impact the test since climate control will be off on both vehicles and both will be preconditioned from wall power prior to setting out. As many of you know, both myself and my fiance have our own Model S's, which puts me in a somewhat fortunate but relatively unique situation where I can easily do side by side tests and comparisons. Test subjects, with notable differences noted: 2014 Tesla Model S P85D, fully loaded except 3rd row seats 21" Silver rims with Michelin Pilot Sport tires, 245/35/R21 in the front, 265/35/R21 in the back Air suspension Just under 1,000 miles on odometer and tires 2014 Tesla Model S P85, my fiance's, also pretty much loaded 21" Grey rims with Continental Extreme Contact tires, 245/35/R21 all around Coil suspension Under 8,000 miles on odometer and tires For the air vs coil suspension, for normal driving this should not effect efficiency. Since I believe the P85D is at an efficiency disadvantage based on my existing data I will have its air suspension set to always low for the test. The sport tires on the P85D are rumored to be less efficient than the tires on the P85. The P85D also has wider rear tires than the P85. I'll see how the final numbers come out. If a reasonable margin for error due to the minor differences makes it too close to call, then well, that is the result. Obviously these are not identical vehicles, but the differences should be minor enough to show any gross efficiency differences that can't be accounted for by the small differences between the cars. I have two GoPro cameras and a dash cam in each car. I plan on syncing the video from all of these and making a four-panel video of the test, possibly time lapsed on the boring parts. The dash cams will view the road ahead. The GoPros will be clipped on the center divider on the pano roof to the left of the driver and aimed at the dash display (this is the plan anyway, but I'll make sure it ends up somewhere that the dash is clearly visible... working on this now actually). The dashes will show the trip meters and the 5 mile energy efficiency graph as the two "apps." I'm still tweaking the details of the trip to make sense, but the plan is to take the same route that includes some non-highway, decent stretch of highway (~20-40 miles), some more non-highway, arrive at a destination, allow both cars to sit for the same amount of time while we're there (the plan is to meet and pick up a couple of friends while we're out that way, one to ride back with each of us), then do the reverse of the trip. The plan will be to use the cruise control on the highway set to various speeds for 5 to 10 miles at a time. I plan to follow the P85 with the P85D for both parts of the trip, also. Combined with the air suspension set to low, I think this should offset any potential differences caused by the different tire configurations. Some things that come to mind for setup for both cars: Ensure cold tire pressures are correct before departure No cabin climate control (jackets, gloves, and seat warmers only) Range mode enabled Sport mode setting on the P85D for acceleration Traction control On on the P85 (should go without saying) All windows closed No cargo Regen set to standard Very limited use of friction brakes No P85(D) shenanigans (ie: acceleration within reason) Charge both cars to 90% overnight, then set both to 95% in the morning After charging, precondition both cars via app at 75F until preconditioning automatically shuts off FLIR pics before departing, at the destination, and when returning If possible I'm going to have Visible Tesla logging for both cars, although the API hasn't been as predictable lately as it used to be for some reason. Should be a pretty fair test I think. Anything else simple to be added to my list to make it as controlled as possible?