Proper fill-up?

[67 Satellite]

Unless I'm out of town, I always fill up at the same pump. I always lock it flowing as fast as it will go,then when it kicks off I round it up to the next 25 cent incriment.

[cems70]

I stop filling when the pump stops. Only rarely am I able to fill up at the same station and pump (which others have noted is the best way to assure consistent fillups). I try to put about 3 - 4 inches of the nozzle into the filler neck, regardless of which station or pump I'm using. I usually accomplish this by pulling the nozzle out of the tank until the bottom most ring at the base of the nozzle spout (I don't know if other parts of the country have this...it looks like a spring wrapped around the base of the nozzle spout) rests on the lip of the filler neck. I then pump slowly to ensure a full fillup with little air mixed in. It's not always a full proof filling method, but it seems to give me relatively consistent results. The pump usually stops as the gas is gurgling at the top of the filler neck (often visible as the pump stops).

Originally Posted by Jay2TheRescue

I always stop at the first click. Overfilling the tank can cause problems with the vapor recovery system on the pump, and recirculate gasoline which will make your mileage appear lower than it actually is. Overfilling the tank can also cause problems with the vapor system on the vehicle as well.

Not true for me. I used to regularly overfill my 1995 Civic VX by as much as 5 gallons. After the pump stopped, I could trickle in another 5 gallons. It never hurt my fuel economy or anything on my vehicle.

[monroe74]

Originally Posted by Jay2TheRescue

Overfilling the tank can cause problems with the vapor recovery system on the pump, and recirculate gasoline which will make your mileage appear lower than it actually is.

Just to emphasize this point and be really clear about what it means: when you overfill, gas will be sucked back into the underground tank, via the nozzle's vapor-recovery system (those little holes near the tip of the nozzle). So you can very easily pay for gas you are not getting. The pump does not calculate a refund when the gas is being sucked back up through the vapor-recovery system!

So yes, this "will make your mileage appear lower than it actually is." And you will also be paying for fuel that you never get to burn.

Originally Posted by cems70

The pump usually stops as the gas is gurgling at the top of the filler neck (often visible as the pump stops).

Gasoline expands when heated. So if you just pumped fuel from a cool underground tank, and then go park your car in the sun, this could create a problem, if you really filled the tank right up to the very top.

I used to regularly overfill my 1995 Civic VX by as much as 5 gallons.

You must mean 0.5, not 5, right?

And even if you're just 'overfilling' by 0.5, I think that means you were probably sending some fuel into the pump's vapor-recovery system.

When the nozzle clicks off for the first time, I'm done.

[Jay2TheRescue]

Yeah, when I was in college and worked at a fuel station we had the station upgraded to vapor recovery. We were told that if you tried to top off the tank that it was possible to pump 20 gallons in a car with only a 15 gallon tank. You're paying for gas that you don't get.

-jay

[froggy81500]

I know about the vapor recovery and the shut off piece on the inside of the hose. Not sure if stations here in NY use the same like I have seen in other states, the nozzles having that boot or whatever over them. We don't have them in NY. I used to work at a station for about 4 years. Occasionally we'd get a nozzle broken where the shut off hose was just hanging inside the nozzle and no longer attached to the end and when that happens the pump keeps kicking off constantly.

[cems70]

Originally Posted by monroe74

You must mean 0.5, not 5, right?

And even if you're just 'overfilling' by 0.5, I think that means you were probably sending some fuel into the pump's vapor-recovery system.

When the nozzle clicks off for the first time, I'm done.

No, I mean 5.0 gallons. I could trickle in another 5.0 gallons after the nozzle clicked off the first time. And I don't think I was sending any fuel into the pump's vapor-recovery system either.

I used to be very good at knowing how much gas was remaining in my tank. So if I filled up the tank, it usually took 9.5 - 9.9 gallons before the nozzle clicked off. If I did not add any more gas after it clicked off, I would get about 510 - 520 miles before my next fillup (if i was getting my usual 54 mpg). If I trickled in another 5 gallons after the nozzle clicked off, I assumed I had about 14.5 - 15 gallons of gas in the tank. And sure enough, I could go about 780 - 810 miles until my next fillup. and my FE was the same 54 - 55 mpg. This tells me that ALL the gas that I trickled into the tank after the nozzle first clicked off was going into the tank, not into the pump's vapor recovery system. When I trickled the gas into the tank, the tip of the nozzle where the holes are was never submerged in the gas in the filler neck. The filler neck gas always settled back down. I was never able to completely fill the tank to the point where I could see the gas floating in the filler neck.

I've always been preplexed by this penomenom in my VX (and now my 1995 Civic DX) of being able to add 50% more gas to the tank.

[monroe74]

Originally Posted by cems70

No, I mean 5.0 gallons. I could trickle in another 5.0 gallons after the nozzle clicked off the first time.

Thanks for responding. This is interesting. I think you once said something about this on another thread, and I appreciate the extra detail you're mentioning now.

And I don't think I was sending any fuel into the pump's vapor-recovery system either.

I agree. I once calculated the maximum possible capacity of the vapor-recovery canister (based on its external dimensions), and it was quite small. Less than a quart, I think.

So if I filled up the tank, it usually took 9.5 - 9.9 gallons before the nozzle clicked off.

Sounds about right. I'm pretty sure your car has a 10-gallon tank. I have the same car, and I once ran the tank dry on purpose, and confirmed that it's 10 gallons.

sure enough, I could go about 780 - 810 miles until my next fillup

Are you sure about the numbers? According to your gas log, your longest tank was 720.3 miles. That's still a lot, though.

When I trickled the gas into the tank, the tip of the nozzle where the holes are was never submerged in the gas in the filler neck.

If those holes are never submerged, then I agree with you that gas is not getting sucked back into the pump's vapor-recovery system.

I was never able to completely fill the tank to the point where I could see the gas floating in the filler neck.

That's an interesting observation. Because at some point it seems that the gas would have to reach that level.

I've always been preplexed by this penomenom in my VX (and now my 1995 Civic DX) of being able to add 50% more gas to the tank.

I agree that it's pretty mysterious. Here's one theory: for some strange reason, your car's tank is 12 gallons, not 10. (Maybe a prior owner did a swap.) I notice in your gaslog that there are only a few times that you pumped over 12 gallons. But your gaslog does indicate you pumped 15 gallons on two occasions. That's definitely a mystery, given that you were careful not to submerge the vapor-recovery holes in the nozzle.

I once pumped 12 gallons into my 10 gallon tank, but I wasn't being careful to prevent those holes from submerging. So I think I was mostly sending gas into those holes.

Anyway, if you learn more about what's happening, I hope you'll share more details.

[cems70]

Originally Posted by monroe74

Are you sure about the numbers? According to your gas log, your longest tank was 720.3 miles. That's still a lot, though.

The gas log you see is for my '95 Civic DX hatchback, not my former '95 VX which I sold 1.5 years ago. You're right that the VX had a 10 gallon tank. I had several 10 gallon fillups after almost running out of gas. I have no explanation about how a 10 gallon tank can take another 5 gallons of gas after the nozzle clicks off. And the same is true for the DX as you saw from a couple of 15 gallon fillups.

[Jay2TheRescue]

Originally Posted by cems70

The gas log you see is for my '95 Civic DX hatchback, not my former '95 VX which I sold 1.5 years ago. You're right that the VX had a 10 gallon tank. I had several 10 gallon fillups after almost running out of gas. I have no explanation about how a 10 gallon tank can take another 5 gallons of gas after the nozzle clicks off. And the same is true for the DX as you saw from a couple of 15 gallon fillups.

Because if you overfill the tank the vapor recovery system on the fuel pump will suck up the excess gasoline if you try to force more into the tank. Once the tank is full if you continue to try to pump fuel you are just recirculating gasoline, and wasting your money.

-Jay

[R.I.D.E.]

cems70;

Looking at your gas log your mileage seems to be consistent with the 15 gal fill ups, so it makes no sense that your fuel was going anywhere but in your car.

If you were pumping any fuel back into the stations tank your mileage would have dropped off dramatically, which it did not.

I have no rational explanation for the 15 gallon fillup, but your average mileage did not change significantly.

I do know that certain vehicles will shut off the pump when there is a lot more room for fuel in the tank. My wifes Murano is that way, to the tune of 2-3 gallons.

In my case when filling I listen for the noise when the fuel starts to build up in the filler neck, stop the pump for a few seconds then finish at about 3/4
speed intil it shuts itself off. I can see the fuel splashing around the opening but I dont have any spilling out of the filler neck.


regards
gary