This is my second Fit and bother were the exact same model. The first one was totaled as I sat at a red light. A pickup (talking on a cell phone) re-ended me going about 35 miles. I was shoved into the car in front of me. Amazingly, I walked away with minor injuries! The passenger zone was completely intact. My insurance adjuster was amazed.

So, I bought another Fit. My second one has never had the gas mileage the first one did and it gives a hard hiccup when I shift from P to R and slight hiccup when I shift from P to D. It's been hesitating when I accelerate and sometimes won't shift at all unless I ease off the accelerater pedal. Also, I've noticed my gas consumption has gone down. I used to get 300 miles on a tank and now it's more like 185-190. My first Fit got 305-310 consistently.

I have 53,000 miles on it. Mostly highway miles.

Is this a big issue? I know nothing about cars and haven't had a chance to take it to the dealer. I bought a 100,000 extended warrenty for it, but figure that with my luck it won't be covered.....

 

Check for the obvious culprits like vacuum leaks for the hard hiccuping (I get a slight hiccup as well from P to anything) and hesitation.

What I can tell you is that you might have gotten unlucky with a bad AT GD3. I personally got only 25-26 mpg average doing 50/50 highway and city, and that was when I was using a ScangaugeII and employing good fuel efficiency techniques. The most I ever got to a tank was 290 miles to a tank of gas, and that was doing 90% highway driving at around 65-70mph. My friend who lives nearby also has a A/T GD3 and he gets over 300 miles to the tank every time, easily. He doesn't know anything about driving efficiently and couldn't care less - yet he gets much better mileage than I do using everything I have and know to get better mileage.

tl;dr A/T GD3 (07-08) have a % of bad/lemon cars that get downright awful mileage no matter what you do. The Honda dealer isn't going to care about your mileage unless a MIL/CEL is on - you're on your own and I'm sorry if you did get stuck with a lemon like I and many others on here did.