MPG Full Tank vs Half Tank or Less

no question, physics, isn't it. i stay between 2 gallons and empty. that means from the flashing pip to zero. and i only add two gallons cause i need to drive 120 miles straight sometimes. also, i remove everything possible from the car that is unnecessary weight. and, i'm on a diet.

one of the best things about the gen 4 is that they eliminated all the storage ares that were gas hogs.

 

you wear a seatbelt? i pulled all mine out to reduce weight.

 

The Eco model dropped ~65 lbs (plus aero improvements) and only got 4mpg

 

30 pounds is less than 1% of the mass of the car plus yourself, so carrying 30 pounds less fuel will reduce fuel consumption while accelerating or on an uphill almost proportionately, i.e., by less than 1%. Any other time, like level cruising, the difference would be a lot less than that 1%.

Yes, you should wait until the tank is closer to empty to refill it, not because that would save significant fuel, but to save yourself the inconvenience of needlessly frequent fuel stops---assuming of course you don't go so far to the opposite extreme that you risk running out of fuel.

 

My wife would be down to 35 MPG if she had me in there.

 

I'd be surprise if the extra mass made much difference. I fill each time, that gives the best point of reference for fuel efficiency.

On a new car, the impurities from the bottom of the tank should be minimal risk.

I'd start with a full tank (I go to the first bowser click, trying to fill at the same bowser each time - not always possible) to enable you to accurately measure fuel use. Fuel gauges and hence computer readouts could be less or more inaccurate at different parts of their scale.

 

To the best of my knowledge, a fuel injected engine maintains a continuous fuel pressure by having the pump run constantly. Fuel circulates constantly from the tank to the injectors and back again. Any fuel not burned is carried back to the tank through a return line. This constant flow would keep the fuel in the tank well mixed and filtered. I wouldn't worry about contents at the bottom of the tank being any different than the top. Besides, the fuel supply comes from near the bottom of the tank anyway.

 

I would test this over several tanks and average. Assuming ambient temperature remains the same or about the same in the trips you take between tanks and between full and half full tanks.
I don't think that 20L/5gal will make a huge difference in fuel consumption so much...hence, try multiple times over several tanks, note the ambient temperature and the routes you do, and see if you can notice such a big difference after all.

 

Previously I have posted GM's rule-of-thumb approximation equation..

I forget the number but let's say less than 1 MPG loss per 100-lbs. So for a 200-lbs me maybe 2 MPG loss. FYI I do not weigh 200-lbs I rounded up.

So the reason I am NOT re-posting GM's equation is that it makes no sense compared Toyota saying Li batt saves 40-lbs and 4 MPG. Something is not adding up.