2008 Scion xB: Pre-Holiday Check? Low Psi

I have found proper psi to be the single biggest contributor to improving gas mileage, besides of course reduced speed. Thank you Edmunds for that article I read some years ago.
 
I had my GMC serviced yesterday at a dealer, and they overinflated by about 5-6 pounds. I find the ride just perfect at the recommended 32 psi. (I have the 17" wheels and am glad vanity did not get the best of me and have to suffer the ride quality of 20"s, and the crazy prices when they wear out sooner.) I do like to go up about 2 psi on a long highway trip, which we will be doing tomorrow. It rides a little stiffer, but I do get about 1-2 mpg better. And when we're camping with the trailer hitch platform loaded, I go up to about 36 in the back.
 
I really like the GM style of TPMS that shows you actual individual pressures on the trip computer, and not just a random warning light when one of them gets too low (by some unknown standard). I imagine I save quite a bit of fuel by checking them every few days and airing up to spec rather than gradually letting them run down to 24 or 25 or wherever it might eventually warn me.

My dealer always tells me during the my 4 month oil changes that they've inflated my tire pressure to 35 PSI per the factory recommendation. Yet when I check the door it clearly says 32 PSI. Very confusing. I agree with ahightower about the tire pressure though. I lose about 10% fuel economy when my PSI drops from 32 to 30.

Hi, Brent. Your blog entry inspired me to check tire pressures this morning before I hit the road. The pressures were pretty low. They rose about 2 psi over the course of the short drive to a local gas station (1 mile at the most) to adjust them. Recommended cold pressures are 33/32 psi F/R. I adjusted them to 35/34 psi F/R. Is there a general rule-of-thumb regarding the difference between hot and cold pressures?
 
I tried looking for articles detailing tire pressure adjustment on the main Edmunds site to no avail.
 
Tire Safety: Don't Ignore the Rubber on the Road
http://www.edmunds.com/ownership/tires/articles/100811/article.html
 
Tires: Traffic Safety Tips
http://www.edmunds.com/ownership/tires/articles/43815/article.html
 
It would be nice if there was a way to access Edmunds' articles easily through Inside Line.
 
All is well on the homefront. I hope you, your wife, and your daughter are having a nice Thanksgiving!

While we're on the topic, what are your opinions of inflating your tires with nitrogen?

Nitrogen is good in theory, but in reality it gives people a false sense of security, and it can get expensive.

Nitrogen - look in the forums for 1000s of opinions. It's a rip-off, pure and simple, no scientific basis for any significant advantage. Let the discussion, chapter XLMCV, begin...

From what I've read, race tires are filled with nitrogen because tire pressures don't fluctuate as much due to temperature differences with nitrogen compared to regular air.

howstuffworks.com is pretty reliable for laymen education.
http://auto.howstuffworks.com/nascar5.htm
 
I wouldn't get nitrogen for my tires.
I don't quite need a constant 43 psi in my passenger car.

Yep, 2 uses for nitrogen: race cars (where precision control of pressures is necessary) and airplanes (where a fire could burst a tire, releasing lots of high pressure air just at the wrong time to fan the fire). Neither applies to street tires.

I'd go with nitrogen... if it was free. I heard some samsclub/ and or cost-co's fill their tires with nitrogen, and will refill for free. If i had that opition I'd take it. otherwise pure waste of money for almost no benifit.