Inflated tires to 40 PSI.

Well I may have been wrong about the "winter gas mixture" causing my mileage to fall. I've noticed that since mid October it's been lower than usual, and have been slowly debugging all the possible causes. Today I finally got around to checking the tire pressure, and they were all sitting nicely at 35-36 PSI. I suppose I can thank my local dealer for that, although the last oil change was in September and I had pretty good mileage all through October.

Anyway, I put them all back up to 40 PSI (cold). I've got about 60 miles left on this tank, so we'll see if the next one improves.

Also, always remember to check the air in your spare tire when inflating the others. I've found the spare tire to be nearly flat in many vehicles, both mine and family member's. A deflated spare tire is useless; you might as well just leave it at home and save yourself the weight and space. In this case mine was fine because I'd checked it previously less than a year ago.