Not always, actually. If you can move at a fairly constant low speed, yes, but if you are in stop and go driving, it can actually eat in to your range more than a constant slow speed. My M/Kwh is almost always lower when I am in stop and go, 5 or 10 mph traffic than when I can cruise at a constant, reasonable, slower speed... The need to accelerate and then decelerate, stopping, and parasitic loses add up in such a condition.
rmerte wrote:One mistaken assumption I see: "and have a 10% remaining margin remaining to allow for possible diversions / traffic jams etc."
Note that traffic jams HELP your range when you're on the freeway. Remember that when you're not moving, you're not using any (relatively) electricity, compared to running a gasoline engine.
TomT +1. On freeways with only gentle up and down grades, destination near same altitude as start, at steady speeds, no climate control, I can achieve 5.1 to 5.2 mi/kwh. Stop and go (0-30 mph) can cut this almost in half, no matter how careful I am to watch traffic several cars ahead of me to smooth-out my speed. In normal traffic I let the speed creep up above 60 mph on short gentle downgrades to avoid the inefficiencies of regen.
Your elevation profile shows some grades that might not be "gentle." On steeper upgrades I would suggest you drop your speed as low as is safe for the surrounding traffic, 50 mph or even lower, to avoid motor draws exceeding 25 kWs. On steeper downgrades you may have to use some regen to keep speed down, otherwise you will have higher aerodynamic losses.
You might consider building the SOC meter (see CanBus sub-forum) to more accurately track you battery State-of-Charge. I find it very helpful for estimating exactly how far I can go and how much reserve I have left.