Variation of predicted kWh among online route planners

[brec]

[This is a cross-posting from my post on the Tesla Motors Club Model S Forum at https://teslamotorsclub.com/tmc/threads/variation-in-predicted-kwh-among-online-route-planners.156386/ ]

Background: on Aug. 10, 2019, I'd like to make a trip from Cal Northern School of Law, Chico, CA, U.S.A., to the Tesla Supercharger at Donner Pass, CA, without charging en route. Question: can I make it with a reasonable margin for safety? I'm the original owner of the car, so I have some experience with road trips.

This is a 132.3 mi. trip with a net elevation change of 5,710 feet.

I used these online trip planners, listed in descending order of their age:
evtripplanner.com ("EVTP")
evtripping.com ("EVTG")
abetterrouteplanner.com ("ABRP")

Results in kWh used:
EVTP: 49.4
EVTG: 52.9
ABRP: 60.7

I tried to make the inputs as equal as possible among the three. Since EVTG uses seasonal weather data and reported a predicted en route temperature of 72.5F, I specified 73F in the other two. I specified a speed multiple of 1.14 or 114% , with the resulting average speeds (and driving times) of:
EVTP: 61.5 mph (2:09)
EVTG: 64.6 mph (2:03)
ABRP: 60.1 mph (2:12)

I figure I can begin the trip with a charge of 90-95%, or about 66-69 kWh. If ABRP's 61 kWh usage result is accurate I'm too chicken to make this trip without an off-route charge en route at Yuba City that would add about 45 min. total to the duration. But if usage of 53 kWh or better is accurate, I'd not charge en route.

I'm curious about the difference is results, and in particular the outlying difference of ABRP from the other two.