[y2kbug]

Whats your favorite and/or most beneficial modification you have done to your car to get better fuel mileage?
I know there is already the 65+ efficiency mod page that kind of answer this question but I'm more interested in your personal opinion and experience.

I started trying to save more gas when i bought my dakota. By putting skinnier tires on it and changing my driving style i was able to maintain a pretty constant 6-8 mpg gain. Unfortunately i am unable to do any better than that.

Since i bought my 1999 corolla ive been fixing and improving things on it in my free time. Just by replacing the old o2 sensor on it i have gained ~10mpg! I have done a few other things on it but it is too soon to tell what effect it has made.
I'm looking to do some modifications on my vehicles to improve their fuel mileage. Thanks!