Weird or normal MPG observation?

[handy]

I finally reached 21.8mpg after remembering to reset after a new fill-up (93 octane at Costco). It was a mix of city and highway and about 20 miles total.

When I was at 16.7mpg slowing down for a stop light it jumped to 17.2 when I completely stopped. After going again it went below 17.2 for a little while before getting higher than 17.2 again. This happened at the next 3-4 stops (increase/decrease/increase). When I got home it was at 21.8.

Has anyone else noticed this? What is causing the sudden increase of @.5mpg when completely stopping?

 

[cvx5832LC]

It's erratic because there's only one tank to average. It settles after a few miles. And it increased as you were braking because techinically you gained fuel (battery charge) as you were slowing down, topping off the "tank".

 

[Tripod1404]

I finally reached 21.8mpg after remembering to reset after a new fill-up (93 octane at Costco). It was a mix of city and highway and about 20 miles total.

When I was at 16.7mpg slowing down for a stop light it jumped to 17.2 when I completely stopped. After going again it went below 17.2 for a little while before getting higher than 17.2 again. This happened at the next 3-4 stops (increase/decrease/increase). When I got home it was at 21.8.

Has anyone else noticed this? What is causing the sudden increase of @.5mpg when completely stopping?

It increases when you are slowing down since engine turns off and you coast. When you accelerate it decreases since engine is working harder. MPG gauge (assuming it is trip based) updates the average mpg after every 200fts or so of new data , so you see the MPG move around on short trips.