Buzzing while turning steering wheel, MPG dropped after gas refill

Hello PriusChat!

The gf and I drive a 2013 Prius Three with 73k miles... We got this car a few weeks ago and we totally love it.

However, I noticed that whenever I'm turning the steering wheel from side to side and the car is parked (like when trying to get out of a parking spot) I noticed a subtle buzzing. This does not happen when I'm turning to the right or the left at highway or street speeds, only when the car is at 0-3 mph.

Video for reference:

Is this sound normal?? Or should I check something?

Another thing that happened is that we had a constant 50/53 mpg consumption and the car has been giving us around 500/520 miles per tank, and on the last full up (it's the second time we fill up the tank, the first time this didn't happened) when I turned on the car, the mpg on the display said 36 mpg.
I freaked out (lol) but after that it's stuck in 47. I'm probably making a big deal out of it because in the mile range it still says that it's going to give me at least 500 miles, But why did this happened? Does it recalculate the mpg every time you fill up The tank?

Thanks for your help and happy Easter!

 

Will do.

I checked the tires and everything seems fine. Don't know what could be happening. Someone told me that it's a normal sound coming from the electric power steering, but I just want to make sure is normal before driving it more and screw something up.

Been googling a lot about electric power steering but haven't going anything about that buzz. And it's weird because it's not like the car feels weird, or it's hard to turn, or make another sound that could indicate a bigger problem, it's just that subtle buzz.

 

Yep, between the two lines .

 

Short period, only When you turn the wheel lock to lock while the car is moving slowly, like parking.