Quote:
Originally Posted by MetroMPG
Agreed 100%!
Plus it's much harder for us to test small optimizations, vs. relatively large changes, since we just don't have the data resolution in coastdown testing or controlled-as-possible A-B-A instrumented runs (eg. based on ScanGauge MPG readings).
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The only reliable method I've found to characterize changes is to average many tankfuls over the same route. Commuting to work is ideal for that, assuming it's substantially useful terrain.
For me, my commute is nearly ideal; Los Angeles to Irvine [yes I'd prefer public trans but Orange County is ideologically allergic to it], flat, smooth steady 55 - 60 mph 3 days a week.
I keep a record (spreadsheet) of every single fillup (every one) noting odometer, etc.
If I want to test a change, I make it then fillup the car, and make a note in the spreadsheet. Then I drive on that change for a couple of weeks, usually 600 miles. That way, fillup/topoff/expansion errors are minimized; even a 1/2 gallon error over dozens of gallons gets swamped.