My 2012 Venza did exactly the same thing. The DTE adapted to the MPG that I was getting. We had a Mazda CX—7, same thing. Both our 2016 and 2019 RAV4 operate the same way.Repeating myself and also some others as well, but I can't agree. DTE is an adaptive system--it adjusts it's readings based on past driving experience. Unless you are driving the exact some places in exactly the same way on every tank, that's going to vary--at least until some time passes and the average driving experience gets worked out.
I get the concern, and it is mixed up in the tank fill issue I agree. But if what I reading indicates people think DTE should be consistent and fixed dependent on how many gallons are in the tank etc. they aren't understanding the system properly.