Do we burn less gasoline by topping off a 3/4 or 1/2 full tank?

Question

Do we burn less gasoline by topping off a 3/4 or 1/2 full tank?

Answer 1

The greater the volume of air in your tank (emptier), the greater the volume of gasoline that will evaporate to fill the air. Evaporated gas cannot be collected and so cannot be brought to the engine to be consumed (burnt), it needs to be liquid.

The weight issue brought up is relevant to consider only when referring to backup (sub) tanks, they should be left empty where possible.

Therefore keeping your tank topped up full will result in the least amount of fuel comsumption.

However the amount of gas you burn remains the same as it is dependant upon factors such as, the air/fuel ratio (burning rich or lean) and how much you rev and load the engine. :P

On a side note, there are a few other tips/rules I have, that can be observed which will drastically reduce your petrolium usage, Shedevil is right.  Email me if you would more info.

Answer 2

Well you would burn less fuel with the lighter the car/truck is, so at half tank. But the amount would be so small it probably wouldnt  be noticable at all.

   Although i know where your coming from, i have heard the keep your car full and youll use less gas, the car burns the same amount for the most point no matter how much gas is in it, only diffrence would be in really large tanks like 100+ gallons and even that probably wouldnt be really noticable. It all has to do with your gas gage. Some stick at certain points longer depending on the instrument not the amount of gas.

  Best way to burn less gas is maintain a constant speed accelerating/decelerating constantly eats up more (why city and highway miles vary). and idling stationary in the newer gas injection cars/trucks that can eat a gallon an hour idle. (where as older cars would use more gas to restart so leaving running was better) also go 50-55 mph to burn less, anything after that the air resistence goes up alot per mph and your car/truck needs to push harder and harder thus burning more and more.

Answer 3

** You never want to so call "Top Off" your tank.  When the nozzle clicks off the pump...most people try to squeeze that extra little bit of gas in there. It was designed to keep people from overfilling and spilling gas everywhere.  The vapor lock it creates as your tank gets fuel is what triggers the shut off, and in turn if you continue pumping past the point that it shut off by itself, it then actually starts sucking gas back out, due to the vapor lock.  It will still register as your getting gas, on the pumps dial, but your probably only getting half of what its saying at that point. I'm not sure if this was what your referring too, but the only term of "Topping Off" I know of, is just that**