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Old 07-11-2012, 10:25 AM   #1451
auskip07
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Quote:
Originally Posted by Haunty View Post
I noticed the first half of the bars go slower, the last half of the bars drop quickly. My last car was like that too.
Every car i have owned seem to do that also. from my 88 chevy blazer to 2012 subaru.
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Old 07-11-2012, 11:25 AM   #1452
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This link goes into it a little saying that the fuel gauges are notoriously inaccurate. I've always noticed the same trend, more miles out of the first half of the tank than the second. According to this it's just the way the gauge reads it. Also, even with the low fuel light on & after I've hit the one bar left & continue to drive past that for say another 20 miles, the tank is certainly not near Empty. When I fill up I get 12.5 gallons at most in that tank so actually at 30mpg there's still be at least another 45 miles I could get out of the tank. So that low fuel light must be calibrated for when there is still 1.5-2 gallons left in the tank. I don't make a habit out of running it to E but that one bar left & low fuel light I'd say gives you at least another 50 miles.
http://auto.howstuffworks.com/fuel-gauge.htm/printable
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Old 07-11-2012, 11:32 AM   #1453
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Quote:
Originally Posted by SleepNMnky View Post
This link goes into it a little saying that the fuel gauges are notoriously inaccurate. I've always noticed the same trend, more miles out of the first half of the tank than the second. According to this it's just the way the gauge reads it. Also, even with the low fuel light on & after I've hit the one bar left & continue to drive past that for say another 20 miles, the tank is certainly not near Empty. When I fill up I get 12.5 gallons at most in that tank so actually at 30mpg there's still be at least another 45 miles I could get out of the tank. So that low fuel light must be calibrated for when there is still 1.5-2 gallons left in the tank. I don't make a habit out of running it to E but that one bar left & low fuel light I'd say gives you at least another 50 miles.
http://auto.howstuffworks.com/fuel-gauge.htm/printable
Owners manual states reserve fuel is about 2.5 gallons, once the light comes on.
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Old 07-11-2012, 11:57 AM   #1454
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Fuel tanks always read E before they are actually empty because the fuel also acts as coolant for the fuel pump. Running out of gas sucks, but then running out of gas and then having to buy another fuel pump sucks even worse than that. Often when people run out of gas, then get more gas into the car, it will not start. Fuel pumps are not cheap.

Also when you really run out of gas, the fuel filter can pickup stuff it would not normally pickup and cause a problem in the fuel filter.

Cars are not like lawnmowers. Running out of gas is really bad for the fuel system.
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Old 07-11-2012, 12:26 PM   #1455
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Which is why I start looking for a gas station at around 300 miles since my last fill up, regardless of how many segments are showing on the gas gauge.
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Old 07-11-2012, 12:41 PM   #1456
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In my experience the gauge will run out and with the light on, it's something like 40 miles left on the display. When I reach 400 miles past my last fill, I look for a station.
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Old 07-11-2012, 12:46 PM   #1457
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I try to never let less than 4 bars appear before I fill up. The reasoning is to prevent pickup of any contaminates they may be in tank.
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Old 07-11-2012, 01:50 PM   #1458
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I had my fuel pump replaced on my last car, it cost over $700 installed, but it was over 100k miles.
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Old 07-11-2012, 02:02 PM   #1459
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Quote:
Originally Posted by Haunty View Post
I had my fuel pump replaced on my last car, it cost over $700 installed, but it was over 100k miles.

Did you run nearly dry or allow some fuel to remain in tank during this 100K?
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Old 07-11-2012, 02:42 PM   #1460
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Quote:
Originally Posted by Impreza1228 View Post
Did you run nearly dry or allow some fuel to remain in tank during this 100K?
90% of the time I filled it at about 1/4 tank left.
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Old 07-11-2012, 06:03 PM   #1461
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The last 3 tank fills all at the same station and same pump at said station, i can add 2.7 gallons after the pump 1st clicks off. I will usually go 100 miles before the first bar turns off. Then Depending on the drive type Which for me is either Normal city or Extreme city. I can get between 10-20 miles per bar through the rest of the tank.
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Old 07-11-2012, 07:40 PM   #1462
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I've been getting 39mpg mixed reliably by not stepping on it too much (manual hatch, '12, premium pkg with no racks). Love this car. I've even been able to get 46 by really, really grannying it.
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Old 07-11-2012, 09:31 PM   #1463
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Quote:
Originally Posted by Impreza1228 View Post
I try to never let less than 4 bars appear before I fill up. The reasoning is to prevent pickup of any contaminates they may be in tank.
The pickup does not float on top of the gasoline. It's at the bottom of the tank.
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Old 07-11-2012, 09:33 PM   #1464
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My first and last bar are very close to 1.5 gallons, while the others are close to 1 gallon. That assumes that my mpg was about the same from the full tank to the empty tank. Since an empty tank is much lighter, that may not be strictly true, though.
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Old 07-12-2012, 09:43 AM   #1465
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Originally Posted by subiTWO View Post
The pickup does not float on top of the gasoline. It's at the bottom of the tank.
What are you saying the fuel pump inlet is at the very bottom of tank and it does not matter?

Therefore running it to reserve is acceptable?

I find that hard to believe, I think that you should not run any car until is at such small level common sense will tell you if anything is at bottom of tank it will be pickup-ed by fuel pump.

We must use common sense logic regardless of where the pickup is located.
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Old 07-12-2012, 11:15 AM   #1466
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There can't be that much sediment in the fuel. I mean it's probably filtered at the refinery, it's filtered at the gas station, and again in your car.
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Old 07-12-2012, 12:20 PM   #1467
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Quote:
Originally Posted by Impreza1228 View Post
What are you saying the fuel pump inlet is at the very bottom of tank and it does not matter?

Therefore running it to reserve is acceptable?

I find that hard to believe, I think that you should not run any car until is at such small level common sense will tell you if anything is at bottom of tank it will be pickup-ed by fuel pump.

We must use common sense logic regardless of where the pickup is located.
My question to you is: how do you think the car can draw down the tank dry, or nearly dry, without feeding from the bottom? It can't.

The fuel pump is siphoning from the bottom of the tank, or near the bottom all the time, regardless of the amount of fuel in the tank. Keeping extra fuel in the tank above where it is siphoned off is not protecting anything. It is not preventing any sediment in the tank from being siphoned out. That's OK - the fuel filter will catch any sediment or particles in the tank - that's why it's there.

You're not harming your engine if you run it with a half-gallon of gas in the tank. The only thing that might happen then is if you make a hard turn, the inertia might make the gas move to the side of the tank away from the gas inlet, and the car might sputter momentarily. (Or more correctly, the car will move while the gas will try to stay in place, causing the gas to be at the side of the tank and away from the fuel inlet).

Last edited by tomwi53092; 07-12-2012 at 12:38 PM.
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Old 07-12-2012, 12:56 PM   #1468
sgoldste01
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How are the fuel pumps in our Imprezas lubricated? I know that in VW TDIs (and other brands too), the diesel fuel provides the lubrication for the fuel pump. But diesel fuel has more lubricating properties (lubricity) than gas, which is why putting gas in a diesel car is so catastrophic. The fuel pump gets destroyed very quickly.

So in a gas car, how is the fuel pump lubricated?
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Old 07-12-2012, 02:40 PM   #1469
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Quote:
Originally Posted by tomwi53092 View Post
My question to you is: how do you think the car can draw down the tank dry, or nearly dry, without feeding from the bottom? It can't.

The fuel pump is siphoning from the bottom of the tank, or near the bottom all the time, regardless of the amount of fuel in the tank. Keeping extra fuel in the tank above where it is siphoned off is not protecting anything. It is not preventing any sediment in the tank from being siphoned out. That's OK - the fuel filter will catch any sediment or particles in the tank - that's why it's there.

You're not harming your engine if you run it with a half-gallon of gas in the tank. The only thing that might happen then is if you make a hard turn, the inertia might make the gas move to the side of the tank away from the gas inlet, and the car might sputter momentarily. (Or more correctly, the car will move while the gas will try to stay in place, causing the gas to be at the side of the tank and away from the fuel inlet).
Not likely to get cavitation with the gas in the tank. I have been autocrossing for years with a minimal amount of gas in the tank taking turns harder than you would on the street. I never had an issue. I did however with power steering fluid.
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Old 07-12-2012, 05:11 PM   #1470
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The fuel tanks are likely baffled like the oil pans are.
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Old 07-12-2012, 05:59 PM   #1471
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The fuel tanks are likely baffled like the oil pans are.
yup....
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Old 07-12-2012, 06:40 PM   #1472
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Best tank so far filled today 14.202 gallons added 393.0 miles driven. (The Low Fuel light was NOT on yet and still showed 2 Bars remained on gauge.)

Calculated 27.7 mpg (Best after 6 fills)
Dash 29.7 mpg avg
A deviation of 2 mpg or 7.2% over
Dash 31 mph avg

E-10( <-- ) 87 Octane Exxon.
I had mixed city driving this tank. instead of mostly extreme city like I usually do. I do Not consider anything within city limits to be highway driving. (even if the road I am on is called a highway)

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Old 07-12-2012, 07:39 PM   #1473
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Quote:
Originally Posted by ZionZR2 View Post
Best tank so far filled today 14.202 gallons added 393.0 miles driven. (The Low Fuel light was NOT on yet and still showed 2 Bars remained on gauge.)

Calculated 27.7 mpg (Best after 6 fills)
Dash 29.7 mpg avg
A deviation of 2 mpg or 7.2% over
Dash 31 mph avg

E-10( <-- ) 87 Octane Exxon.
I had mixed city driving this tank. instead of mostly extreme city like I usually do. I do Not consider anything within city limits to be highway driving. (even if the road I am on is called a highway)

whoa! 2 bars remaining and you filled in over 14 gallons. do you do a big top off after the first click?
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Old 07-12-2012, 07:48 PM   #1474
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Quote:
Originally Posted by nubsub

whoa! 2 bars remaining and you filled in over 14 gallons. do you do a big top off after the first click?
Topping off is dumb and in some vehicles can damage vapor recovery (aka emissions) equipment.

I don't think (actually I am pretty positive, but too lazy to search the owners manual to correct a practice that I don't do) Subaru or any other manufacturer recommends it.

If you are driving in remote areas without gas stations maybe, but for your typical commute it is dumb, just like wanting to force the car into 1st gear above 20mph is dumb.

I'm always left scratching my head and wondering how so many dumb practices are being talked up on this forum. But it's your car, do what you think is excellent.
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Old 07-12-2012, 08:15 PM   #1475
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Quote:
Originally Posted by Zeeper
I'm always left scratching my head and wondering how so many dumb practices are being talked up on this forum. But it's your car, do what you think is excellent.
Nubsub wasn't saying he/she did, just asking how someone could fill to 14.2 gallons. I'm always left scratching my head and wondering how so many people feel the need to call people dumb and school all of us on what they assume us little people don't already know.
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