I'm new to the Insght world having just bought a 2000 5 speed with 134K miles on it. So far I love the car! I drive 150 miles a day and I am getting 70+ mpg. I have been really trying to hold my right foot steady at a given MPG level and I have noticed that for some reason while holding the throttle very steady I feel a "surge" and the MPG either goes up or down about 10-15MPG. It almost feels like the A/C compressor is cycling on and off but I have it turned off. Could this be the engine going in and out of lean burn? If so, how can I keep it in lean burn or why does it go back and forth? Many thanks!!