Whew. It appears you and the rest of us are indeed the victims of a miscalculation scam of some kind, but first of all let me say that if you use gasoline that has ethanol the gasoline burns up faster. We put it in our big 1989 Olds wagon and started burning rubber out of traffic lights. The darn stuff has more power but it also burns up faster. The flow rate or something must have been altered, which MAY HAVE thrown off your onboard computer detection.

I liked the other fellow’s comment about how your Honda system must be only showing mpg for when the car is moving. If true then your gauge is really showing you TWO THINGS and isn’t a scam at all, only by using a calculator able to see it. The gauge is giving you an accurate readout for MOVING MILEAGE in order to help learn the driver how to pump the accelerator pedal LESS HARD LESS OFTEN. The more you drive like a retired schoolteacher the better mpg you get. INDIRECTLY also telling you how much time you’re spending sitting in traffic, at traffic lights, etc.

So what you would really need to do is fill the gas tank and drive a straight 30 minutes to an hour on the interstate at 60 miles per hour then stop and fill the tank and compare what the readout on the gauge is showing to what the calculator tells you was burned.

I imagine the numbers will be a lot closer. But if there’s still a slight discrepancy I would then conclude the Honda Civic may not be calculating correctly and could in fact be from the amount of ethanol in your gasoline. The way to check that of course would be to fill the tank with non-ethanol gas and do the test again but for the entire tank this time.

It’s a shame they don’t do it and then tell all their car buyer’s the results because without being honest they end up losing Sales. People are getting really fed up with junk like this and then not being treated correctly when you brought the issue to their attention… because on the surface it really looks like to most people (who aren’t sleuths like you) that the readout was purposely set to show the highest possible number, making the Honda Civic User feel good so they’ll come back and buy another one later.

But if it’s just a matter of telling you the driver how much waste time you’re spending on the highway, that actually has value to let you know you need to find another route or time to do your driving. I’m a fellow sleuth like yourself and have been solving some right sticky energy & environmental issues for years. I finally in 2008 made a special page that contains my very best work. Give a visit sometime =>

http://www.askinventor.com/pdflistfor2008.htm .
…. ClimateEngine (Woody Riley)