car using more fuel after 1/2 tank

[98outbackpdx]

when ever my tank gets to 1/2 it just starts gulping the gas.
i can do 200 miles of all highway, on a half tank, but after that it goes down like a rock.
the most i have squeezed out of a tank was 310 miles of all highway, it took 12.xx gallons on the 310 miles tank.
today it went from 200 miles on a half tank but i have done 260 miles on this tank and it is down to 1/4 of a tank tonight at 260 miles.
anyone else have this problem?
at a half tank it takes about 8 gallons. so i know it is pretty accurate.

[TheAngryPidgeon]

The reason for this is that auto manufacturers design the gas tank in a funneled manner towards the bottom of the tank. Pardon the crude graphics, but this is somewhat how it looks:
__
| |
|_/

It would be far more expensive and complicated to design a gauge that accurately portrays the exact percentage of fuel left in the tank, so they just use a float that measures how much of the tank is full. Therefore the bottom 1/2 or so seems to go more quickly, because it is actually less than half of the tank.

:smt023

[StatGSR]

^ what he said, if you filled your tank when it read 1/2 a tank, you would see that your average mpg would be the same. If anything your car is using less gas as the tank goes empty as there is less weight in the car to move around.

[chuckthefuk]

How far do you take the needle? To the E? To the bottom Peg?
-Chuck

[green97gt]

seems like every time i hop in the wifes 97gt the tank is on E, just how much father can it go?

theres a thick white bar on the E side and its always on the bottom of the white bar, ill have to look for the peg.

[chuckthefuk]

It all depends on the cluster + sending unit + fuel pump.

To average all BD/BK/BG the rule of thumb is

IF! Your needle is sitting on the empty PEG the little peg that prevents the needle from falling past the lowest point. And you Gas Light is on then you usually have 10 liters or 2.64 galons left. An approx 50-70 KM left to roll on.

I tell everyone who is worried about your the fuel consumption to carry a Jerry Can with them and fill up when your car starts to sputter. You'll be surprised how long you can drive for on just fumes.

-Chuck

[jey]

when ever my tank gets to 1/2 it just starts gulping the gas.
i can do 200 miles of all highway, on a half tank, but after that it goes down like a rock.
the most i have squeezed out of a tank was 310 miles of all highway, it took 12.xx gallons on the 310 miles tank.
today it went from 200 miles on a half tank but i have done 260 miles on this tank and it is down to 1/4 of a tank tonight at 260 miles.
anyone else have this problem?
at a half tank it takes about 8 gallons. so i know it is pretty accurate.

It's not really gulping any more gas. Based on your numbers you went 200 miles on 8 gallons, and then 4.xx more gallons to go the next 110 miles, so that's pretty consistent. What's happening is the gas gauge gets inaccurate below 1/2 tank, which is the way both my BK Legacies behaved. Obviously when you filled up a "full tank" and only put 12.xx gallons in you really had a bit more left.

Basically we have alarmist gas gauges :lol:

[Huffer]

Good grief. Not another fuel & mileage thread. ...

[97scoob]

Good grief. Not another fuel & mileage thread. ...

haha when i saw this thread i was like wow, everytime i check this forum there is a new gas mpg thread :shock:

[98outbackpdx]

sorry i have a hard time making things clear, i have done 260 miles on 1/4 of a tank my latest one, the 310 miles was from driving back from california about a month ago.

[StatGSR]

no, we understand that.

the math proves nothing is wrong with your mileage... 8/12 = ?/310 ?=206 which is what you get at half a tank.

the difference that your seeing is is that the first half on the gauge that you see is ~ 8 gal, the next half that you see on the gauge is ~4 gallons.

[Reuben]

Welcome to the wonderful world of fuel gauges. I've said this a million times in these types of threads

In the aviation world, we have a saying. The only time a fuel gauge reads accurately is when it's dead full, or dead empty.

Also, it's commonly known, at least on clubsub, that the last half of subaru tanks always goes quicker than the first. Car doesn't change economy, it's just the way the gauge works.

[Da Brat]

Thanks guys for this healthy discussion...my GT was kinda acting the same and it had me wondering...not any more.....cool stuff

[Huffer]

and enough. We know the gas gauge moves quicker in the 2nd half, but is not accurate. Done.