Instant fuel economy fluctuates?

[tw627x]

I tried searching and didn't see anything, so excuse me if this has been discussed. I went on a 45 mile trip today on the interstate. I don't go out of town often so I haven't really seen this happen. While im cruising, no hills, the instant fuel economy never sits still. Its always bouncing between 15-22. I feel like it should be able to be a lot more steady as Im cruising at one speed on flat ground. Anyone else experience this?

[SILVER SLED]

Welcome to the reality of how an engine uses fuel.

[tw627x]

That may be the case and that's why I posted to find out. I understand different motors, but my Malibu at least stays at the same reading for more than a second and doesn't jump 5mpg every second. Its a little concerning. Especially since I can't get above 19 mpg average

[redwngr]

Malibu is using a longer average and/or not updating the display as often.