When I test drove the HCH2 at the dealer, I cleared the average mpg gauge and I was able to get the gage to give me 50+ mpg within a minute or two of driving. With my car (a different vehicle than the test drive), I zeroed the average mpg gauge this morning, start driving, and it initially gives me 16 mpg. It goes upwards quickly. Right now it says 40.8. Granted I only drove 15 or so miles in total today, but it looks like the gauge in my car doesn't calculate in the same way as the test drive car. Watching the realtime gauge during my trip tells me that I am doing much better than 40.8 so I know it will continue to rise.

Any ideas?

Perhaps when you got 50 MPG right away the car was going downhill and warmed up.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

This is mid-Michigan. There are no hills

Warmed up? I don't believe so. I played with all the controls before driving and I'm fairly sure the engine temp was cold.

What do you mean by 'cold'? I've noticed that it makes a difference whether the car has been sitting overnight or has been driven within the last couple of hours.

Cold meaning no bars on the engine fluid temp gauge.