i hear that u can get better gas mileage if u let the gas tank run dry half way rather than all the way and then refill it all the way. is this true? i hear things like the air in the tank has alot to do with the extra consumtion. ne1 heard about this?

 

No. Quite the opposite.
I have had betterluck running the tank down to 1/8-1/4 tank before refill. Remember please that fuel adds weight, and weight costs power and mileage... nearly 8lbs/gal. Say, 7.25 gals left in the tank when you refill, that's+/-58 lbs of dead weight.Add another 7.25 gals and now you have 116lbs just sloshing around back there. Add to that that you'd be filling it up and running full more of the time, approx 1/3 of the time more than now and that adds up to quite a bit!!
Run it down a little lower (not too low though.Remember the fuel pump needs to be kept cool) and now your only dragging around half of that weight, or less. That should result in slightly better mileage and performance.

Why do you think they do that in race cars? They'd run 'em on fumes all the time if they could.

 

To answer your question of air and fuel. I think you might of heard that fuel evaporates with the heat. Not much though.

 

The fuel systems in modern cars... for that last 20 yrs or so, are closed. Fuel that evaporates re condenses and is sent back to the tank as liquid.

 

I believe they are vented, to prevent pressure build up.

You would know about cars 20 years ago, though.

 

The moderator is correct again.

Found this.

FUEL TANK
Tank location and design are always a compromise with available space. Most automobiles have a single tank located in the rear of the vehicle. Fuel tanks today have internal baffles to prevent the fuel from sloshing back and forth. If you hear noises from the rear on acceleration and deceleration the baffles could be broken. All tanks have a fuel filler pipe, a fuel outlet line to the engine and a vent system. All catalytic converter cars are equipped with a filler pipe restrictor so that leaded fuel, which is dispensed from a thicker nozzle, cannot be introduced into the fuel system. All fuel tanks must be vented. Before 1970, fuel tanks were vented to the atmosphere, emitting hydrocarbon emissions. Since 1970 all tanks are vented through a charcoal canister, into the engine to be burned before being released to the atmosphere. This is called evaporative emission control and will be discussed further in the emission control section. Federal law requires that all 1976 and newer cars have vehicle rollover protection devices to prevent fuel spills.

 

ahhh i didnt take the weight factor into account. very true. but rich u say that u shouldnt let it run dry all the way.. i end up forgetting to fill up and it goes DOWWWWWNNNN.. like past "E" lol.. is that a problem?

 

Your fuel pump is electric. It lives inside the fuel tank. It's essentially an electric motor with a rotory pump @ one end. It depends on the fuel flowing around it to helpkeep that motor cool. If it overheats, it burns up.Simple as that.

Got $250-$350 to spend?? (I'm guessing, as I don't really know what they cost for sure.)

Yeah, I'd break that habit of letting it run down too low all the time. I'd leave, and I usually do leave 2-3gals in the tank when I fill up. 10-12gals at fill up, and often less than that.

 

ahh.. i did not know that. thank you very much sir :-).