Trip computers try their best to forecast range but can easily be caught out, whether EV or ICE, as all they have to go on is the amount of fuel in the tank (or charge in the battery), and recent consumption (or driving style).
They forecast the future consumption - and therefore range - based largely upon what has happened in the past. It would be able to estimate range more accurately if the destination, route and live traffic conditions were all known too.
On Friday I refilled my petrol car, and immediately after refilling the range was 400 miles - after driving a further 20-30 miles the range was up to 480 miles, so at that time the car thought that more than 500 miles was possible on a full tank.
Before refilling I was driving on relatively free-flowing 30 mph roads, and after refuelling I was driving steadily on a free flowing mostly 40-50 mph road. When I refuelled it assumed that I’d carry on driving as I had before, at 30 mph. After driving at 40-50 mph for a while it assumed I’d carry on doing that.
In reality nether happened. There’s absolutely no way that that car could manage 500 miles on a single tank in real world driving, but if I had carried on driving in exactly the same way in exactly the same conditions then I might have got closer than what actually happened.
In practice I joined a motorway - driving at 70 mph - and the range fell much faster than the distance being covered. I didn’t check at the end of my journey but I would estimate that the range would have been around 360-380 miles for the full tank.
Had I driven to the motorway, met you at the junction and swapped cars with you completing the journey in my car, it would be easy to conclude that the range forecast by the trip computer cannot be trusted. At a point in time - with constant driving conditions - it’s pretty accurate.
