Wow, an awful lot of gas vapors would have to be escaping past that gas cap to make a significant difference in gas mileage on a car that's probably only getting 15~18 MPG to begin with. Your mileage may have improved but I'd be more likely to believe it's because you're getting more used to driving the car and aren't suffering as severely from 'new Mustang happy feet'. Get a small notebook to keep in the car and write down your odometer reading and how many gallons you put in every time you fill it up. That's the only way you're gonna know for sure what's going on with your gas mileage. I put the date too and then off to the side I can make any notes about repairs, maintenance, upgrades or if I had to add any fluids so I can look back and have a record of all that stuff or see if there's any trends going on.
Haha. Well in Austin they were forecasting snow in the morning which I immediately called on and what do ya know. I wake up and its not snowing. We'll see what happens through the rest of the day. And yeah I'm not really sure about my gas mileage exactly. I typically have other things I'm thinking about than recording it specifically. What caught my concern was how quickly I seemed to go through a tank of gas compared to my 99 grand cherokee that I recently sold, and that didn't get good gas mileage too. But yes it could be that the gas cap was insignificant and I've just gotten better at controlling the RPMs in first gear now or something. But I certainly don't try and fly off the line at every stop light, even when I first got the car. I didn't really have the time to try and diagnose the problem, and I also just assumed that was just how the gas mileage was going to be but that I wasn't used to it. The gas cap thing just arose at the inspection and it seems, compared to the trend of gas usage before the inspection, that it may have helped.
