I experimented with this(nothing hardcore just comparing tank averages) running several tanks with 5 gallons compared to the usual 15 gallons with no noteable increase in FE. It does accelerate better but I didn't like filling up every 3-4 days.
Not surprised it didn't show up as a measurable increase.
If we take the conservative side of EPA's claimed 1-2% FE penalty from 100 lbs extra weight, then you'd increase your fuel economy by .3% if you drove around with 30 lbs (5 gals) less fuel in the tank. That's easily lost in the noise, even with instrumentation.
But it's still a real gain. Weight reduction is common sense.
Zug: do you know this 10-15% FE improvement because of a scanguage, or because of the way your fuel gauge reacts? Because fuel gauges are notorious for reading "non-linearly" and their gradations shouldn't be trusted.
My gas gauge is crapped out for the most part....I go by tank refills.
Leading the perpetually ignorant and uninformed into the light of scientific knowledge. Did I really say that?
a new policy....I intend to ignore the nescient...a waste of time and energy.
The problem of water condensing in a mostly empty gas tank is a problem that we used to have in the pre-emission control days when the gas tank was vented directly to the atmosphere through an air vent tube that ran from the top part of the tank to the underside of the car. This tube allowed air to enter the tank as gas was used up by the ICE (it could also pump 1/2 gal of fuel overboard if you parked the car on a steep side slope with a full tank in the hot sun as the remaining air in the tank heated, expanded, and pushed the fuel out through the tube). The water accumulation problem occured when the tank was mostly empty and the car was left out in the hot sun in a climate with a high relative humidity. Each day the air in the tank would expand, venting out through the tube, then each evening as the air cooled, it would pull humid outside air back into the tank. As the temp in the tank dropped below dewpoint, water in the humid air in the tank would condense and run down into the bottom of the tank. Given enough days parked in a humid location and you could accumulate enough water to kill your ICE the next time you drove your car. Also the water accumulation could rust a hole through the bottom of the metal fuel tank (no plastic tanks back then). I've had both of these things happen to me with my 68 VW Beetle.
the o2 sensor adjusts the fuel air mix by sniffing the exaust, so when vapor is being burnt as it is vented from the charcal canister, it should reduce the amount of liquid fuel being injected, and altho you are then burning more vaporized fuel, the fuel left in your tank is that much closer to being varnish.
it would be interesting to mesure fender hight befor and after filling your gas tank to find out exactly how much it affects ride hight, mesure both front and back to see how weight is shifting as well.