My car blows...
 

Literally, not figuratively...little pun. But anyway, whenever I remove the gas cap when it's about empty a bunch of air rushes out. It kinda scared me at first since I've never seen anything like it but I've come to terms with it and now I want to know if releasing the built up pressure (or whatever it is) will improve the mpg. I have a friend that swears the air in an almost empty tank will make a car consume more fuel. Doesn't make much sense mechanically but he made better grades than me in school so who am I to say he's wrong. But would my 7 be more fuel efficient if I let some of the air out every once and awhile?

hugh
 

no it will not - you friend is wrong

Yeah the fuel tanks needs to be pressurized to adequitely deliver fuel. Your friend knows absolutely nothing about cars LOL

what part of NC are you from?

Its just vapor pressure! nothing big! Hell just becuase you make better grades in school dont mean shit! In the real world you are judged on your GPA or what grades you made.

It is ****possible**** that it could cause worse MPG, BUTTTT alot of other things would actually have to be wrong with the fuel system. In short though... your friend is wrong.

The hotter it gets the more your going to notice a *whosh* when you open the cap... normall, nothing to worry about unless you like to smoke when you fill up.

The vapor pressure of an alcohol is less than that of water. The buildup of the gas is from vaporized gas which turns into a gasous state due to:

1. Heat from driving the car
2. Being able to vaporize easier in the tank as the liquid gas is consumed and tank volume allows for the increased vapor
3. Pressurized gas tank for fuel delivery
.....

It shouldn't be a problem. Just don't stick you eye up to it when you remove the fuel cap! :)

cult's car blows him....... lol!!! WTG!!! :jump:

swoosh from gas tank. too much pressure. stabilizing itself.

let car run without gas tank for about 6 minutes

lol i dont think that the car can run without a gas tank nicholas.

Your emissions system isn't working correctly. The vapors are supposed to go to the charcaol canister, with the hydrocarbons being absorbed there. Either the canister is old and plugged, or removed and the tank line has been capped off.

Your friend is incorrect, unfortunatly, so are most of the previous posts.