I just completed a 200 mile round trip on the interstate today in my CVT Civic Hyb.
Although I did not determine the exact amount of error in my trip meter, it seems to be running around 3% slow, which would translate into better actual mileage. This all assumes the mile markers are correct. Would like comment from others. My car is an 05 with less than 700 miles on it.

I'm not sure what you're comparing to. Is this in comparison to your GPS?

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It seems to me that on all the cars that I've had, the odometer always measures the distance slightly differently than the mile markers on the highway.

As your tires wear down it'll become 'fast'. Its common to most cars as you've said. Look at the bright side, if you can go a little over the speed limit and still be legal

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No GPS. Measuring trip meter against interstate mileage markers.

i doubt those markers are that accurate

Were the mileage markers over a large distance? Like in Arizona, when you cross from California, there are mileage markers every mile, at least until you get to Phoenix, well over 100 miles.

I would imagine those to be pretty accurate, and a good comparison point for the car's odometer.

Mileage markers are every mile except for a few missing ones and at interchanges.
I just covered the same route in my CRV and it tracked almost exactly with them. The rear tires are about 60-70% worn on it.

It sounds funny suggesting your tripometer is more accurate than that of a government highway vehicle, but based off what you said about your CRV, I'd say that's exactly it. Mile markers aren't measured out on foot with tape; they're marked off one by one with a dash of spraypaint on the road out the passenger's side opened door as a very slow-moving vehicle counts them on its own odometer. If (as is very likely) whatever vehicle measured that stretch of highway wasn't sporting a brand new set of tires like those on your HCH, then its measurements probably did come out a hair fast, which is why most drivers never notice a difference...how often do any of us actually have 4 new tires on devoid of any of the wear-and-tear that can cause slight miscalculations?