I brought my car in for an oil change last week (yes, I can change my own oil, more on that later) and ever since I had been noticing that my mileage was off about 1.5 mpg. My mileage on my commute to work is fairly consistent, so I noticed it right away. Then I remembered seeing the guy putting air in the tires, so i check the pressure, sure enough, they ranged from 27-30 (sticker calls for 32). Fixed it before I left work today, and the mileage is back.
At least I know I'm paying attention.
And yes, I can change my own oil, but. On my Escort the filter is between the block and the firewall and it is nearly impossible to remove without spilling oil, no matter how big a drain pan I use. I live at an apartment building so the only place I have to work on cars is at my parent's house in the driveway. My mom already got po'd at me for spilling oil once, I don't want to lose the use of my "garage". So I hunt around for one of the repair chains running a special for like $20 or so. The oil and filter cost about $11 anyway. I go to a repair place rather than a quick lube so at least a real mechanic is working on the car. I always change my own oil on the Firebird, which is a lot easier to work on.