Three weeks old and a few firsts!

I believe there's actually like a rubber gasket around the opening, so it may indeed be creating a small vacuum as you pump gas -- be carefully pulling it out as a lot of people have had issues with gas spills if you don't let the bladder settle a little bit after filling all the way up.

Could be... could be weather as well -- could be you're learning to drive the car a bit better as well.

Folks reccomend 40 in the front and 38 in the back... as long as the front is 2psi higher than the rear, you're good. But the more air in there (within specifications), the less roll resistance. You are sacrificing a bit of traction, but probably not too noticable.

Good question.

 

I'm in the Pocono's and I run 42front, 40 in rears. The jump in mpg's is probably because you are learning more about your Prius and the last week has been alot warmer here. Where in Pa. r u?

 

As cold as it is now I doubt the tire will warm up in that short distance unless you are speeding. Feel the tire, cold. At least it is cold here in Arizona!

1 or 2 #'s I wouldn't worry. Do a search here if you have all day to read a ton of posts on pressure and refueling.

I run 40f/38r. Got down to 34 once and highway milage suffered.

 

Just do the math. If LF is 38 and you want to run at 38/36, leave it alone, even if it read 39 if you re-checked it at the gas station. If, OTOH, you want to run at 40/38, inflate it 2 lb., even if the reading has gone up to 39. That'll make it 41, but it should cool back down to 40 later.

As was said, the tires probably won't warm up that much in 3 mi.

If going to the gas station to do this is a pain, especially in winter, consider buying a cheap, small air compressor so you can add air at home. There are several for sale now that plug into your car's accessory receptacle---$20-30.