[MetalMK]

Hi all,

One day, my friend told me that you cannot overfill your gas tank, it is really bad for some kind of sensor inside, but I do this all the time because I always pay with cash and by doing that I get lesser change back ($58-$60, $54-$55). But is my friend right? That I have been destroying some kind of sensor in my gas tank by filling up half a litre more gas?

[Sportstick]

Originally Posted by MetalMK

Hi all,

One day, my friend told me that you cannot overfill your gas tank, it is really bad for some kind of sensor inside, but I do this all the time because I always pay with cash and by doing that I get lesser change back ($58-$60, $54-$55). But is my friend right? That I have been destroying some kind of sensor in my gas tank by filling up half a litre more gas?

You have been drowning the evaporative canister in gasoline designed to prevent fumes from escaping by topping off the tank. When the handle first clicks off, that's the time to stop.

[aerobod]

The evaporative system can be damaged and require repair if raw fuel reaches the carbon filter. There should be a check valve to stop this happening, but it is only a risk if fuel is forced into the system after the pump cuts off on the first click when filling the fuel tank.

[MetalMK]

Originally Posted by Sportstick

You have been drowning the evaporative canister in gasoline designed to prevent fumes from escaping by topping off the tank. When the handle first clicks off, that's the time to stop.

Originally Posted by aerobod

The evaporative system can be damaged and require repair if raw fuel reaches the carbon filter. There should be a check valve to stop this happening, but it is only a risk if fuel is forced into the system after the pump cuts off on the first click when filling the fuel tank.

Thanks, I am going to stop overfilling the gas tank, but what are the signs of a failing "evaporative canister" because if anything happens to the it, WARRANTY!!!

[aerobod]

Check engine light with an evaporative system failure code(s), engine stalling and limp mode are possibilities.

[Sportstick]

Originally Posted by MetalMK

Thanks, I am going to stop overfilling the gas tank, but what are the signs of a failing "evaporative canister" because if anything happens to the it, WARRANTY!!!

Unfortunately not....will be a clear indication of not following the owner directions not to top off the tank.

[Rayscott]

Not worth the risk to save a few $$ and void the warranty.

[MetalMK]

Originally Posted by Sportstick

Unfortunately not....will be a clear indication of not following the owner directions not to top off the tank.

What direction?

[Sportstick]

Originally Posted by MetalMK

What direction?

Owner's manual.

[stevenvillatoro]

Originally Posted by Rayscott

Not worth the risk to save a few $$ and void the warranty.

I'm not sure how overfilling the tank could save money, since fuel economy is unrelated to tank capacity. Maybe I missed your point? :

[M235SDCA]

Originally Posted by Sportstick

Unfortunately not....will be a clear indication of not following the owner directions not to top off the tank.

This is correct. I have an F10 and was going to bring it in thinking the charcoal canister was plugged. SA told me exactly that - if there is evidence of overfilling it is NOT covered under warranty.

[Sportstick]

Originally Posted by stevenvillatoro

I'm not sure how overfilling the tank could save money, since fuel economy is unrelated to tank capacity. Maybe I missed your point? :

I think it's a desire about not having much change to carry around...he rounds closer to the next dollar bill increment he's carrying. Of course, a credit card would be a simple solution.

[albertw]

The only way to find out how much the car's computer is exaggerating your gas mileage is to fill it until it won't take any more. I've done that several times on trips with every car I've owned and never had a problem.

I also learned that pumps vary a lot - after the first click there's between 2 and 10 liters of space left. For a car with a small gas tank that can affect range significantly. Except when I'm checking consumption I run it at half speed after the first click until it clicks twice again. Then there's usually near 2 liters of space left.

I think the only real issue is that the gas comes out of the ground cold. If you fill right up and drive only a short distance before parking it there isn't enough space in the tank to hold the gas as it expands while warming to ambient.

Anyone know what "eslide" means?

[MetalMK]

Originally Posted by albertw

The only way to find out how much the car's computer is exaggerating your gas mileage is to fill it until it won't take any more. I've done that several times on trips with every car I've owned and never had a problem.

I also learned that pumps vary a lot - after the first click there's between 2 and 10 liters of space left. For a car with a small gas tank that can affect range significantly. Except when I'm checking consumption I run it at half speed after the first click until it clicks twice again. Then there's usually near 2 liters of space left.

I think the only real issue is that the gas comes out of the ground cold. If you fill right up and drive only a short distance before parking it there isn't enough space in the tank to hold the gas as it expands while warming to ambient.

Anyone know what "eslide" means?

So if I continue to fill my tank after the first click, it is going to click twice when it's almost full?

[Sportstick]

Originally Posted by MetalMK

So if I continue to fill my tank after the first click, it is going to click twice when it's almost full?

No, it's one click each time the pump stops, but the sound of that second click will be you covering a non-warranty repair at some point. Despite the owner's manual, you're still pursuing this course of action?

[MetalMK]

Originally Posted by Sportstick

No, it's one click each time the pump stops, but the sound of that second click will be you covering a non-warranty repair at some point. Despite the owner's manual, you're still pursuing this course of action?

No I am not, I just want to convince myself that I was not damaging my car

[Sportstick]

Originally Posted by MetalMK

No I am not, I just want to convince myself that I was not damaging my car

The reality is that you did damage your car if you filled up to the point where the canister became full of gasoline. However, given that gasoline is volatile, it may have evaporated, depending on how much and how often. This, we will never know. If you stop the practice, and just drive and no driveability issues arise and the Check Engine Light is off, you probably escaped unharmed for the long term.

[Ron Jeffries]

the car thinks it knows its mpg. is it wrong?

[Maynard]

It 'knows' mpg by having good measurement of how much fuel gets injected (and by my #'s this is pretty accurate). But it is fairly wonky about range remaining - a combo of guessing how much is left in the tank, and what your mpg will be (I think it guestimates using your lower recent mileage - on long highway trips w/ higher average, it shows longer range for about the same amount of remaining fuel). I doubt that it has a very accurate way to measure tank contents.

Not worth the risk, IMHO. I sympathize with wanting a few more miles from this tiny little tank, and I think there are some safeguards that at least try to prevent sloshing out, but the hassles of plugging an evap canister will make it seem like a huge waste.

[albertw]

Of course the car "knows" how much gas you used and how far you traveled. But, does it tell you the truth or some % better as demanded by marketing? For example, my '05 Altima gave 5% worse mileage on the highway and 10% worse in town than the computer claimed. The only car I've had that was right on is my '01 Corvette, probably because the mileage is so amazingly good that there's no need to lie about it.

[omera60]

Originally Posted by albertw

Of course the car "knows" how much gas you used and how far you traveled. But, does it tell you the truth or some % better as demanded by marketing? For example, my '05 Altima gave 5% worse mileage on the highway and 10% worse in town than the computer claimed. The only car I've had that was right on is my '01 Corvette, probably because the mileage is so amazingly good that there's no need to lie about it.

They are changing the way they get these numbers to reflect much more accurate ones, especially for the ones claimed by the factory. One of the new cycles main aims is also it tries to globalize this test as it is mostly country or union based and have different requirements from each other.

This is the old test cycle for EU:

https://en.m.wikipedia.org/wiki/New_..._Driving_Cycle

And this is the new one;

https://en.m.wikipedia.org/wiki/Worl...Test_Procedure