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Old 10-12-2012, 05:54 AM   #9 (permalink)
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Originally Posted by wmjinman View Post
One thing I'm wondering about is whether the ScanGauge is accurate for mpg BEFORE the 2nd fillup "calibration".
Most likely not.
Though the relative results will still remain after calibration.

2) I never dreamed 40 mph would be the "peak efficiency speed".
The results from 35-45 seem to be in the same ballpark, though it could well be your car's most FE speed is 40.

At reasonable speeds though.
Depending on gearing, it may well be 20 mph ... at idle rpm in a high gear.

Road-testing for FE is tricky, as things change along the way - often beyond your control.
What we perceive as flat isn't always so flat either
To do this really right, one'd have to measure the exact same stretch of road every time (from a milepost or a sign to another such landmark).

Site-starter MetroMPG has a thread on how to do road testing the right way - or as right as the road will allow you to test - ( )

Personally, I don't do dedicated tests.
I do try out things on my regular commute.
If it works, it'll show on the gauges and ultimately show up in the fuel stats.
Strayed to the Dark Diesel Side

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