A couple weeks ago, I finally stopped by Costco's tire shop to get my tires topped off. They'd been looking low for a couple months, but I never could remember to get them checked. Since we had bought the tires at Costco about 2 years ago, they checked them and topped them for free (I had to show my receipt, which luckily I had in the glove compartment).
Anyway - since then, I've noticed that the car runs much smoother and vibrates less. But I've also noticed that the fuel efficiency has improved. Usually I get about 270 miles to a tank of gas (10 gallons). But right now I'm at 175 miles on the trip odometer, and the fuel guage is at the halfway point. If this trend continues, I might get over 300 miles to this tank of gas.
I know that keeping your tires correctly inflated is always listed as a way to improve your fuel efficiency, but I didn't expect it to make this big a difference!!
The other small change I've made recently is that I no longer drive so far looking for my favorite kind of parking space in the garage at work. I used to pass by all the spots on the uphill ramp right after I entered the garage, instead going up to the second level to find a non-sloped spot. Since the garage levels are one way, this meant that I had to drive all the way around the level to exit, even if my spot was very close to the top of the uphill ramp. I measured it on my trip odometer, and discovered that I was adding 2/10 of a mile to my trip every day by doing this. Over the course of a week, that was a mile, and over the course of a year, that was probably two gallons of gas. So now, instead of shunning those sloped spots, I take the first one I can find. Every little bit helps!