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Okay, so I nurse 180 mile tank at around 53 MPG finally!!! Then drive 6 miles in the city catching 8 reds on an uphill incline and drop my MPG to 46 MPG (according to the readout) for 7 minutes of time. Now, 200 miles later, of pure freeway driving where the I-MPG reads average of 75 MPG (everytime I look at it, nearly constantly)... and I've only made up to 48.5 MPG. I also had 3 coworkers in the car with me.
It it really possible to be at 53 MPG and have a few (minor) accelerations drop you by 8 MPG and require 200+ miles of perfect hypermiling to make it back up? Perhaps the readout isn't really very accurate? Because, by that logice, if I did it 10 times or so, I'd be on an empty tank but that doesn't happen.
Whey is it so *easy* to lose many MPG just by catching even 1 red, and it is nearly impossible to make it back up?
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I believe a lot of this is the deceptive nature of using "MPG" as a unit, instead of gallons per [100] mile, which is more intuitive for figuring out actual cost. The difference between 10 and 20 mpg is 3 gallons after 100 miles. Conversely, going from 50mpg to 100mpg will only save 1 gallon, but looks more significant than going from 10-20 on a linear MPG graph.
Or, look at it this way, if you go up a hill at 20mpg, and back down the same way with the engine off (infinite MPG), the best you can possibly average is 40mpg.
(180mi)/53 MPG = 3.40 gallons consumed
After the red lights you were at:
(186)/46 MPG = 4.04 gallons
That means you'd have to have burnt .64 gallons, or about 10mpg which seems extremely high. If you spent an equal time accelerating, and braking (unlikey), you'd have to have averaged 5MPG on the display for that to be correct, which would be hard even doing repeated 0-60-0 cycles up an incline...