[HonestPessimist]

Hey, I know a guy who told me that the best way to save money on gas is to drive the vehicle until it's half-full, then get to a gas station and fill up the rest in the tank, so to save a lot of money in the process every week. This way, he says, you won't have to pay for the whole thing if you fill up the whole tank.

Is this an economy efficient approach or what? Half price for half-filled tank? Is it okay on the vehicle's engine with a half-full tank all the times?

Just wondering.

[sjruckle]

This is my first post! Yay!

Anyways, the emptier your tank, the better fuel economy you will get, because there is less weight (in the form of unused fuel) to lug around. If you don't like running around with a nearly-empty tank all the time, then the better option (assuming that the gas prices are going to constantly rise) is to fill up your tank just before you think a particular station's prices are going to go up. That way you've always got the cheapest fuel in your tank. Most vehicles will run fine no matter where you keep the tank level, but you should fill up every once in awhile so you can prevent condensation from forming in the top of the tank. Water rusts fuel pumps.

[rogerhb]

Apparently most people drive around with half-filled tanks.

The advantage of having only the fuel you need in the tank for a trip is you are not hauling around gallons (kgs) of fuel around, basically a weight issue. Remember fuel is basically a kilogram per litre.

It is not good driving around close to empty because crud floats to the top of the petrol, as you run your tank down you start pulling the crud in through you carburettor which gunges it up.

If the price of fuel is going up continually then keeping the tank topped up means you are always driving around with petrol you bought a few days ago, hence you are actually running on cheaper fuel.

However, if everybody decides to fill up to the brim this then puts an extra strain on the delivery pipeline, suddenly there is a surge of demand that was not there previously (think of everybodies car times half the volume of their fuel tanks).

[sjruckle]

I was actually talking about someone who was telling me that driving around with a half-full tank improves gas mileage somehow. He said it wasn't because of the weight reduction. He probably didn't know what he was talking about.

What crud? Maybe water, but water sinks to the bottom of the tank below the fuel, as well as anything that is water-soluble.

I just fill up every two days, whenever I get around to it. My tank almost never drops below the 3/4 line. Just in case I need to drive somewhere very far in a hurry..

[pilferage]

Taking that air freshener out of your car improves mileage...
but not by much.
Same goes for running on half a tank versus a whole tank. Additionally, I've heard this can hurt your mileage if your fuel pump is going out.