harmful to top the gas tank on 2013 avalanche?

Rkh · Mar 2, 2014

My last thread I ask about the computer readout for the mpg, but was wondering maybe if I fill the tank to the very top, computer readout would be more accurate. I have heard your not suppose to top tank -any thoughts?

Royse · Mar 2, 2014

If you over-fill it by topping off you can get gas into the vapor
canister. For an '02 Avalanche that canister is $250. Last month.

Janicholson · Mar 2, 2014

My thoughts. If you are doing a gas milage test with a corect, or factored to correct odometer (using a five mile highway post check to assess accuracy) and fastoring in error, then filling at the same fill pump using the same nozzle, and letting it shutoff automatically aanndd putting the nozzle into the tank the same direction each time. will get you real fuel use figures. Not high science with calibrated flow meters, but pretty darn good. Topping up is using tiny repeated squirts to fill the neck of the tank plumb full. not best practices on the evaporitive emmissions system. Jim

jm. · Mar 2, 2014

That is not going to change your inboard reading. I would venture to bet that the computer is closer to actual that your computing it. Really hard to do the pencil thing unless you just pick a millage fill the vehicle and drive add fuel and keep a record of the fuel added , then after two or three tanks go back to the same setting at the same station and try and fill to the same level. Then add all fuel and divide by miles traveled. Ever one I have had for the last several years was pretty accurate.

Brent Zappe · Mar 2, 2014

Back when I worked in pumping gas at a gas station (back in 1980). We where told by the person who owned the station that filling the car tank to the top was some thing not good to do. It could fill the vapor control canisiter with raw gas and then it could work it self in to the ventalation system for the car makeing the people smell gasoline vapors. The pump nozels are design to take the vapors of the gas tank but over filling the tank the pump nozel will suck the gas back like it does with the vapors. Not a good ideal.

Stephen Newell · Mar 2, 2014

Even if you have a old car filling the tank to the top on a cool or cold day the gas can expand when it warms up and run out on the ground. The price of gas today I don't think anyone wants to see that.

David G · Mar 2, 2014

I think the mileage is computed from the injection volume, not the tank level.

Anonymous-0 · Mar 2, 2014

Royce is right.

504 · Mar 2, 2014

Just fill to the pump clicks off, roll up to the even number if paying cash. I fill on the slowest setting.

Bob · Mar 2, 2014

"I think the mileage is computed from the injection volume, not the tank level."

And the injection volume is computed by the 'puter monitoring engine speed and the duty cycle of the injectors.

So the fuel actually used isn't really MEASURED.

The number the 'puter comes up with will only be perfectly correct if all the injectors are absolutely at exact flow "spec", and the gas temp/specific gravity is exactly what the system was calibrated at.

So, the mileage the 'puter shows you is actually an "educated guess".

A while back, some rumors were going around that certain aftermarket "chips" achieved better mileage on the "digital dash" by mucking with the software the 'puter uses to calculate MPG.

Whether true or not, I'm sure that would be possible.

David G · Mar 2, 2014

I would agree

mj · Mar 3, 2014

(quoted from post at 19:34:31 03/02/14) Even if you have a old car filling the tank to the top on a cool or cold day the gas can expand when it warms up and run out on the ground. The price of gas today I don't think anyone wants to see that.

Everything in moderation, as they say.
AND, if you have an in-tank fuel pump, try to keep it at least 1/4 full to keep the pump cool (especially in the summer) Gas is no cheaper in the ground than in the tank. 8)

NEBeef · Mar 3, 2014

(quoted from post at 04:05:59 03/03/14) "I think the mileage is computed from the injection volume, not the tank level."

And the injection volume is computed by the 'puter monitoring engine speed and the duty cycle of the injectors.

So the fuel actually used isn't really MEASURED.

The number the 'puter comes up with will only be perfectly correct if all the injectors are absolutely at exact flow "spec", and the gas temp/specific gravity is exactly what the system was calibrated at.

So, the mileage the 'puter shows you is actually an "educated guess".

Now I don't know for sure, I'm just pondering here... but I'm going to guess that the computer is pretty accurate - or at least *could* be pretty accurate. The amount of fuel injected is adjusted to get the correct engine parameters based on temperature, O2 output, etc. So if you have an injector that, let's say, dumping a little too much fuel then the computer will (or could) back that injector off a bit. So the measure of overall fuel usage would be based on how the nature of the actual combustion, not just an estimate of injector calibration. Now all of that is, of course, based on the accuracy of many sensors.

Again, I'm not sure it *is* that way, but the computers have enough smarts to do that. And of course if you're getting lousy mileage because you have a leak in your fuel tank, then measuring what goes is a better method...

DENNIS MIN · Mar 3, 2014

mj,

Last fuel pump I replaced had an aluminum cup surrounding the fuel pump. It filled whenever the pump ran, giving the pump some cooling.

2001 Saturn.

D.

harmful to top the gas tank on 2013 avalanche?

Rkh

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Royse

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Janicholson

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jm.

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Brent Zappe

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Stephen Newell

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David G

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Anonymous-0

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504

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Bob

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David G

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mj

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NEBeef

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DENNIS MIN

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