I hope I'm not repeating a topic here, but I've observed some odd behavior between my two trip meters. Here's the scenario:

I reset Trip A after each fill-up, so it gives me the MPG on the current tank. I leave Trip B alone so it shows MPG over all the tanks I've used. Here's what's weird: Last time I filled up, Trip B (all tanks) said 47.0 mpg. Trip A (current tank) showed under 47 mpg for the first half of the tank and was slowly inching up until it reached 46.8 MPG. At that point, Trip B went to 47.1.

Now, my understanding of averages is that if you have an average and you're adding new values to that average, the average won't go up unless what you're adding is greater than the average. So, in this case, why did Trip B (all tanks) go up when the values being added were below the average?

Or am I missing something?

 

Greetings;

In the time before you stopped, you were getting instantaneous mpg readings higher than the averages in both trip memories. Both are increasing there averages (this is when having 100ths would be revealing) but at a different rate due to the mileage they're tracking as well.
You just observed the .1 level event, while the .01 events would have been "normal". I noticed this behavior as well and agree that it does raise an eyebrow. Just wait till your instantaneous mpg is between the two trips, they'll move in opposite directions if watched long enough.
Just my 2.00 cents