can anyone tell me how to access the lifetime mpg in the car

You can't it's the one thing software-wise I'd like updated more than anything - having a lifetime mpg on the display, since the tank mileage on the consumption screen will auto-reset after fillups.
You have to do it by hand.

 

I gotta agree. They take more screen space to present less information than the simple LED display from my old Saab.

How about a Distance Until Empty number? They could also give you MPG for a trip. Estimated Fuel needed for a trip, etc.

I'd also like a car info screen that gave me Oil pressure, oil temp, water temp, Engine RPM, 12V battery charge level.

 

At least engine temp. I have often found problems before they became major from the temp guage, like thermostats stuck open. Not only that, but I would be able to tell when my mileage should be up to nominal because warmup is complete.

Also current cabin temp would be nice. Just because the HVAC is set to 72, doesn't mean the cabin reached that temp.

 

Ah, but a distance to empty readout would necessitate the addition of a reliable gas gauge!

Accessing lifetime MPG is really a very straightforward, two-step process:

1) Note your current odometer reading
2) Using your saved fuel receipts (you did save them, didn't you?), divide the sum of all gallons put into the tank into the current odometer reading.

Knowing cabin temperature is even easier. Just glance at the $2 thermometer pinned to your sun visor.

Joking about temperature aside, I imagine that one reason Toyota omitted the internal temperature readout is because of the "fuzzy logic" used by the HVAC system to second-guess the driver's temperature setting. When set to 72 degrees, the HVAC aims for a temperature that it thinks will "feel like" 72 degrees. Depending on solar radiation, external temperature, and the planetary alignments of Jupiter and Saturn, the actual internal temperature might be significantly higher or lower than 72.

Just imagine how many service inquiries that sort of knowledge would generate...

 

At first xevious, I didn't know how the HVAC using fuzzy logic would cause a problem with an incabin temp reading. Then I realized what you were getting at. If the HVAC determined that 70 or 74 was a better temp for you to feel the 72 degree setting you set, and people saw that, they would complain. Good point. Still want the reading.