I have a quick question. I have an 07 Civic Hybrid, on my 65 mile commute to work each day the is a point in the freeway that has a very slight left bend that goes downhill, slightly but it is downhill. At this point my MPG gauge in the dash moves from around 50MPG to 1 dot(zero). No charge is showing up, which I have noticed if I am in any type of turn charge and MPG goes down lightly. I usually always drive with cruise control. At this point if I either hit the gas or brake the MPG gauge jumps to over the 50 MPG mark. Strange to me. I was wondering if anyone knows why it does this.

 

Since you always run with cruise and it's happening in the same spot, it might be a purge cycle. Lean burn mode periodically requires a purge cycle to clear out the cat.

Tomorrow, try dropping out of cruise a couple miles before you get to the curve. Modulate the throttle manually and try to accelerate just a little. Before you get to the curve, try to get your entry speed back to normal with cruise engaged.

If it repeats as usual, Im full of it. If you get a different (higher) mileage reading, I might be right.