Issue with MPG monitor or just outlier?

[Bm93]

I've only tested once so far as I'm new to this, but I was finding out my average MPG to and from work but only on the motorway. I cruise controlled 55mph the entire way both ways, morning and evening.

Morning, temp was -1.5c at entry, +0.5c at exit. I averaged 50.4MPG (according to cars readout) I was driving east.

After finishing work, temp stayed at 1c either end, and I averaged 46.7mpg, driving west.

Elevation at home side is 430ft, work side is 424ft, so insignificant in the grand scheme.

Is this an issue with the readout, or would it be due to direction of travel? I never had to adjust speed at any time.

I plan on doing it for an entire week to get an average but wanted to ask anyway.

[Piotrsko]

Two trips do not make accurate data, at least from an ex instrumentation tech point of view.
Lots of data amalgamates into a trend line which tends to seperate the odd data to discard and shows measurement errors

Was one trip an anomaly? You don't know, yet.

[JRMichler]

Check the wind. A barely noticeable wind can easily make that much difference. As an example, see the coastdown test results for my old 06 Canyon: https://ecomodder.com/forum/showthre...yon-20405.html.

[Bm93]

Yeah, figured as much. I'll keep doing it and see how it flattens out over time.