Again, like others said - the MPG reading on the display is anywhere from 5-10% off, so manual is really the way to figure what you're getting. But, the display is helpful if you keep that in mind - it does get you in the ballpark.
Typically the MPG on the display in my 4Runner is 12-13% higher than when manually calculated.
When I tow my trailer, the MPG on the display does go down to around 10% higher than calculated which I always found interesting.
As far as getting better MPG goes, Momentum is your friend. I learned that early on when I first started towing my trailer.
Getting almost 6K lbs of trailer moving and keeping it moving is all about looking far down the road, seeing potential driving situations
well before you reach them and prudent use of the brakes. All that impacts the momentum of a vehicle (and trailer).
The same holds true for just driving the 4Runner. If I look down the road and see a red light or a line of cars that are stopped I will
take my foot off the gas and let my momentum carry the 4Runner forward then gently apply the brakes as needed.
I have already paid for that momentum so to speak so why not use it?
Continuing on the gas then jamming on the brakes to stop at the last minute wastes momentum, gas and brakes.
Steady acceleration from a stop instead of stomping on the gas and drag racing also helps MPG.
Bottom line, a person's driving style and how they react to different driving situations can have an impact on the MPG they can achieve.